OCR Additional Science C4a Chemical Patterns

OCR Additional Science C4a Chemical Patterns
21/09/2018

The structure of the atom
The Ancient Greeks used to believe that everything was made up of very small particles. I did some experiments in 1808 that proved this and called these particles ATOMS: Dalton ELECTRON – negative, mass nearly nothing PROTON – positive, same mass as neutron (“1”) NEUTRON – neutral, same mass as proton (“1”) 21/09/2018

Mass and atomic number 4 He 2
Particle Relative Mass Relative Charge Proton 1 +1 Neutron Electron Very small -1 MASS NUMBER = number of protons + number of neutrons He 2 4 SYMBOL PROTON NUMBER = number of protons (obviously) 21/09/2018

How many protons, neutrons and electrons?
Mass and atomic number How many protons, neutrons and electrons? 1 11 16 H B O 1 5 8 23 35 238 Na Cl U 21/09/2018 11 17 92

Spectroscopy Compounds containing lithium, sodium, potassium, calcium and barium can be recognised by burning the compound and observing the colours produced: Lithium Red Sodium Yellow Potassium Lilac 21/09/2018

Periodic Table Introduction
21/09/2018

Horizontal rows are called PERIODS
Periodic table Mendeleev The periodic table arranges all the elements in groups according to their properties. Vertical columns are called GROUPS Horizontal rows are called PERIODS 21/09/2018

Most of the elements are metals:
The Periodic Table Most of the elements are metals: These elements are metals H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Fe Ni Cu Zn Br Kr Ag I Xe Pt Au Hg These elements are non-metals This line divides metals from non-metals 21/09/2018

The Periodic Table (Most important) All of the elements in the same group have similar PROPERTIES. This is how I thought of the periodic table in the first place. This is called PERIODICITY. H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Fe Ni Cu Zn Br Kr Ag I Xe Pt Au Hg E.g. consider the group 1 metals. They all: Are soft Can be easily cut with a knife React with water 21/09/2018

Sodium + water sodium hydroxide + hydrogen
Balancing equations Consider the following reaction: Sodium + water sodium hydroxide + hydrogen Na O H O H Na + H + This equation doesn’t balance – there are 2 hydrogen atoms on the left hand side (the “reactants” and 3 on the right hand side (the “products”) 21/09/2018

Balancing equations We need to balance the equation:
Sodium + water sodium hydroxide + hydrogen Na O H O H Na O H Na O H + H + Na Now the equation is balanced, and we can write it as: 2Na(s) + 2H2O(l) NaOH(aq) + H2(g) 21/09/2018

Some examples 2 2 3 2 3 Mg + O2 Zn + HCl Fe + Cl2 NaOH + HCl CH4 + O2
Mg O2 Zn HCl Fe Cl2 NaOH HCl CH O2 Ca H2O NaOH H2SO4 CH3OH O2 MgO ZnCl H2 FeCl3 NaCl H2O CO H2O Ca(OH) H2 Na2SO H2O 2 21/09/2018

Hazard signs to learn… Acid Corrosive Toxic h i Harmful Irritant
Oxidising 21/09/2018

Group 1 – The alkali metals
Na K Rb Cs Fr 21/09/2018

Group 1 – The alkali metals
Some facts… 1) These metals all have ___ electron in their outer shell. 2) Density increases as you go down the group, while melting point ________ 2) Reactivity increases as you go _______ the group. This is because the electrons are further away from the _______ every time a _____ is added, so they are given up more easily. 3) They all react with water to form an alkali (hence their name) and __________, e.g: Potassium + water potassium hydroxide + hydrogen 2K(s) H2O(l) KOH(aq) H2(g) Words – down, one, shell, hydrogen, nucleus, decreases 21/09/2018

Properties Element Melting Point (OC) Boiling Point (OC)
21/09/2018 Element Melting Point (OC) Boiling Point (OC) Density (g/cm3) Lithium 180 1340 0.53 Sodium 98 883 0.97 Potassium 64 760 0.86 Rubidium 39 688 1.53 Caesium 29 671 1.90

Group 7 – The halogens F Cl Br I At 21/09/2018

Group 7 – The Halogens Some facts… Decreasing reactivity
1) Reactivity DECREASES as you go down the group (This is because the electrons are further away from the nucleus and so any extra electrons aren’t attracted as much). 2) They exist as diatomic molecules (so that they both have a full outer shell): Cl Cl 3) Because of this fluorine and chlorine are liquid at room temperature and bromine is a gas 21/09/2018

Properties Element Melting Point (OC) Boiling Point (OC)
21/09/2018 Element Melting Point (OC) Boiling Point (OC) Density (g/cm3) Flourine -220 -188 0.0016 Chlorine -101 -34 0.003 Bromine -7 59 3.12 Iodine 114 184 4.95 Astatine 302? 337? ??

Displacement reactions
To put it simply, a MORE reactive halogen will displace a LESS reactive halogen from a solution of its salt. Potassium chloride KCl(aq) Potassium bromide KBr(aq) Potassium iodide KI (aq) Chlorine Cl2 Bromine Br2 Iodine I2 F Cl Br I Decreasing reactivity 21/09/2018

OCR Additional Science Chemical Patterns C4b

Electron structure 39 K 19 Consider an atom of Potassium:
Nucleus K 19 39 Potassium has 19 electrons. These electrons occupy specific energy levels “shells”… The inner shell has __ electrons The next shell has __ electrons The next shell has the remaining __ electron Electron structure = 2,8,8,1 21/09/2018

The Periodic Table Elements in the same group have the same number of electrons in the outer shell (this corresponds to their group number) H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Fe Ni Cu Zn Br Kr Ag I Xe Pt Au Hg These elements have __ electrons in their outer shells These elements have __ electrons in their outer shell E.g. all group 1 metals have __ electron in their outer shell 21/09/2018

As you move down through the periods an extra electron shell is added:
The Periodic Table As you move down through the periods an extra electron shell is added: E.g. Lithium has 3 electron in the configuration 2,1 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Fe Ni Cu Zn Br Kr Ag I Xe Pt Au Hg Sodium has 11 electrons in the configuration 2,8,1 Potassium has 19 electrons in the configuration __,__,__,__ 21/09/2018

Trends in Group 1 Consider a sodium atom: +
Take away one of the electrons (oxidation) Sodium ion Now consider a potassium atom: + Take away one of the electrons (oxidation) Potassium ion Potassium loses its electron more easily because its further away – potassium is MORE REACTIVE

Trends in Group 7 Consider a flourine atom: -
Add an electron (reduction) Flouride ion Now consider a chlorine atom: - Add an electron (reduction) Chloride ion Chlorine doesn’t gain an electron as easily as flourine so it is LESS REACTIVE

++++ ---- Electrolysis Positive electrode (anode)
Negative electrode (cathode) ++++ ---- Cu2+ Cl- Solution containing copper ions (cations) and chloride ions (anions) Cu2+ Cl- Cu2+ Cl- 21/09/2018

Ionic Bonding Cl Hi. My name’s Johnny Chlorine. I’m in Group 7, so I have 7 electrons in my outer shell Cl I’d quite like to have a full outer shell. To do this I need to GAIN an electron. Who can help me? 21/09/2018

Here comes my friend, Sophie Sodium
Ionic Bonding Cl Here comes my friend, Sophie Sodium Na Hey Johnny. I’m in Group 1 so I have one electron in my outer shell. I don’t like having just one electron so I’m quite happy to get rid of it. Do you want it? Okay - + Cl Na Now we’ve both got full outer shells and we’ve both gained a charge. We’ve formed an IONIC bond. 21/09/2018

This is called an ion (in this case, a positive hydrogen ion)
Ions An ion is formed when an atom gains or loses electrons and becomes charged: + - The electron is negatively charged The proton is positively charged + + If we “take away” the electron we’re left with just a positive charge: This is called an ion (in this case, a positive hydrogen ion) 21/09/2018

Ionic bonding Na Cl Na + Cl -
This is where a metal bonds with a non-metal (usually). Instead of sharing the electrons one of the atoms “_____” one or more electrons to the other. For example, consider sodium and chlorine: Sodium has 1 electron on its outer shell and chlorine has 7, so if sodium gives its electron to chlorine they both have a ___ outer shell and are ______. A _______ charged sodium ion (cation) A _________ charged chloride ion (anion) As opposed to covalent bonds, ionic bonds form strong forces of attraction between different ions due to their opposite ______, causing GIANT IONIC STRUCTURES to form (e.g sodium chloride) with ______ melting and boiling points: Na Cl Na + Cl - 21/09/2018

Some examples of ionic bonding
Cl - Magnesium chloride: Cl Mg 2+ Mg + Cl - Cl MgCl2 Calcium oxide: O Ca + 2+ 2- 21/09/2018 CaO

Balancing ions Some common ions:
Sodium – Na+ Potassium – K+ Magnesium – Mg2+ Ammonium – NH4+ Chloride – Cl- Bromide – Br- Oxide – O2- Sulphate – SO42- Determine the formula of the following compounds: Sodium chloride Magnesium oxide Magnesium chloride Ammonium chloride Sodium sulphate Sodium oxide

OCR 21st Century Science Unit C5a Revision

The Earth’s Atmosphere
21/09/2018 The Earth’s Atmosphere Present day atmosphere contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.04% CO2 Carbon dioxide, water vapour Oxygen Nitrogen Noble gases

Chemicals in the Air Chemical Structure Diagram Boiling point/OC
21/09/2018 Chemical Structure Diagram Boiling point/OC Melting point/OC Oxygen, O2 O=O -183 -218 Nitrogen, N2 N=N -196 -210 Carbon dioxide, CO2 O=C=O -78 No liquid state Water vapour, H2O H-O-H 100 Argon. Ar Ar -186 -189

More about Forces 1) Forces between molecules:
The forces between each molecule are very weak so the molecules can easily be pulled apart – this means they will have low boiling points. 2) Forces within the molecule: Forces within the molecules are very strong due to the electrostatic attraction in a covalent bond caused by the protons attracting electrons. Each line represents an electron being shared between the atoms

Other ways of drawing molecules
21/09/2018 Consider ammonia (NH3): H N H N H N 21/09/2018

The Hydrosphere Most of the Earth’s surface is water – we call this the “hydrosphere” and it consists of lakes, oceans, seas and rivers. These features contain lots of dissolved compounds called salts. 21/09/2018

The Structure of salts – “a lattice”
Cl- Na+ When many positive and negative ions are joined they form a “giant ionic lattice” where each ion is held to the other by strong electrostatic forces of attraction (ionic bonds). If these ions are strongly held together what affect would this have on the substance’s: Melting point? Boiling point? State (solid, liquid or gas) at room temperature? 21/09/2018

Chemicals of the hydrosphere - Water
21/09/2018

Dissolving a crystal lattice
+ - + - + - + - + - 21/09/2018

Dissolving Ionic Structures
When an ionic structure like sodium chloride is dissolved it enables the water to conduct electricity as charge is carried by the ions: Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ 21/09/2018

Precipitation Reactions
21/09/2018 A precipitation reaction occurs when an insoluble solid is made by mixing two ionic solutions together. Method: 1) Mix the reactants together 2) Filter off the precipitate 3) Wash the residue 4) Dry the residue in an oven at 50OC 21/09/2018

Solubility rules The following guidelines are useful in working out if a substance will dissolve: All common sodium, potassium and ammonium salts are soluble All nitrates are soluble Common chlorides are soluble but not silver and lead Common sulfates are soluble but not those of lead, barium and calcium Common carbonates and hydroxides are insoluble except those of sodium, potassium and ammonium 21/09/2018

CaCl2 + 2NaOH Ca(OH)2 + 2NaCl
Precipitates Some metal compounds form precipitates, i.e. an insoluble solid that is formed when another ionic substance is added to them. Consider calcium chloride and sodium hydroxide: CaCl NaOH Ca(OH)2 + 2NaCl Ca OH Ca(OH)2 What precipitates are formed with the following metal compounds when they react with sodium hydroxide? Metal compound Precipitate formed Soluble or insoluble? Colour Calcium chloride Calcium hydroxide White Aluminium chloride Magnesium chloride Ammonium chloride

Testing for chloride and sulfate ions
For each test state: 1) The colour of the precipitate 2) What compound it is Test 1: Chloride ions Add a few drops of dilute nitric acid to the chloride ion solution followed by a few drops of silver nitrate. Precipitate formed = silver chloride (white) Test 2: Sulphate ions Add a few drops of dilute hydrochloric acid to the sulphate ion solution followed by a few drops of barium chloride. Precipitate formed = barium sulphate (white again) 21/09/2018

Testing for carbonate ions
Limewater Limewater turns milky/cloudy Calcium carbonate + hydrochloric acid calcium chloride + carbon dioxide + water 21/09/2018

Metals Metal atoms are very closely packed together in a regular arrangement. The atoms are held together by metallic bonds that cause the metal to usually have high melting and boiling points.

Properties of metals Metals have very high melting points (which means that they are usually _____) whereas non-metals will melt at lower ___________ All metals conduct heat and __________ very well, whereas non-metals don’t (usually) Metals are strong and ______ but bendable. Non-metals are usually _____ or they will snap. Metals will _____ when freshly cut or scratched, whereas non-metals are usually dull. Metals have higher _______ than non-metals (i.e. they weigh more) Metals can be used to make ______ (a mixture of different metals) Words - alloys, electricity, solids, weak, densities, temperatures, tough, shine

Words – slip, electrons, melting, electricity, strong, ions
A closer look at metals + Metals are defined as elements that readily lose ______ to form positive ____. The ions are closely packed (hence the metal is ______) and they have strong bonds holding them together (hence the high _______ points). The presence of free electrons means that metals can conduct ______. Metals can bend because the layers can “____” over each other: Words – slip, electrons, melting, electricity, strong, ions + + + + + + + + + + +

C5 Chemicals in Nature C5b 21/09/2018

The Earth The lithosphere, the outer layer of the Earth, is made up of a mixture of minerals 21/09/2018

Giant Covalent structures (“lattices”)
Notice that giant covalent structures have very different properties to individual covalent molecules: 2. Graphite – carbon atoms arranged in a layered structure, with free _______ in between each layer enabling carbon to conduct _________ (like metals) 1. Diamond – a giant covalent structure with a very ____ melting point due to ______ bonds between carbon atoms 3. Silicon dioxide (sand) – a giant covalent structure of silicon and oxygen atoms with strong _____ causing a high ______ point and it’s a good insulator as it has no free electrons O Si Words – melting, high, electrons, bonds, strong, electricity

Using Covalent Structures
21/09/2018 Form of carbon Property Uses Why? Carbon – diamond Very hard Drill tips Extremely strong covalent structure Graphite Soft, conducts electricity Lubricants and making electrodes Graphite is arranged in layers that can slide over each other and it contains free electrons.

Elements in Rocks A lot of the silicon and oxygen in the lithosphere exists in the form of silicon dioxide (sand) 21/09/2018

“Reduce” the oxygen to make iron
Extracting Metals Some definitions: A METAL ORE is a mineral or mixture of minerals from which it is “economically viable” to extract some metal. Most ores contain METAL OXIDES (e.g. rust = iron oxide). To “extract” a metal from a metal oxide we need to REDUCE the oxygen. This is called a REDUCTION reaction. To put it simply: Oxide Iron Iron ore “Reduce” the oxygen to make iron 21/09/2018

Increasing reactivity
How do we do it? Potassium Sodium Calcium Magnesium Aluminium Carbon Zinc Iron Tin Lead Copper Silver Gold Platinum Increasing reactivity Metals ABOVE CARBON, because of their high reactivity, cannot be extracted using carbon Metals BELOW CARBON are extracted by heating them with carbon. This is a “displacement reaction” Carbon Oxide Iron Carbon + iron oxide carbon dioxide + iron These LOW REACTIVITY metals won’t need to be extracted because they are SO unreactive you’ll find them on their own, not in a metal oxide 21/09/2018

Mass and atomic number revision
21/09/2018 Mass and atomic number revision Particle Relative Mass Relative Charge Proton 1 +1 Neutron Electron Very small -1 MASS NUMBER = number of protons + number of neutrons He 2 4 SYMBOL PROTON NUMBER = number of protons (obviously) 21/09/2018

Relative formula mass, Mr
The relative formula mass of a compound is the relative atomic masses of all the elements in the compound added together. Relative atomic mass of O = 16 E.g. water H2O: Relative atomic mass of H = 1 Therefore Mr for water = 16 + (2x1) = 18 Work out Mr for the following compounds: HCl NaOH MgCl2 H2SO4 K2CO3 H=1, Cl=35 so Mr = 36 Na=23, O=16, H=1 so Mr = 40 Mg=24, Cl=35 so Mr = 24+(2x35) = 94 H=1, S=32, O=16 so Mr = (2x1)+32+(4x16) = 98 K=39, C=12, O=16 so Mr = (2x39)+12+(3x16) = 138 21/09/2018

Calculating percentage mass
If you can work out Mr then this bit is easy… Percentage mass (%) = Mass of element Ar Relative formula mass Mr x100% Calculate the percentage mass of magnesium in magnesium oxide, MgO: Ar for magnesium = 24 Ar for oxygen = 16 Mr for magnesium oxide = = 40 Therefore percentage mass = 24/40 x 100% = 60% Calculate the percentage mass of the following: Hydrogen in hydrochloric acid, HCl Potassium in potassium chloride, KCl Calcium in calcium chloride, CaCl2 Oxygen in water, H2O 3% 52% 36% 89% 21/09/2018

Recap questions Work out the relative formula mass of:
21/09/2018 Recap questions Work out the relative formula mass of: Carbon dioxide CO2 Calcium oxide CaO Methane CH4 44 56 16 Work out the percentage mass of: Carbon in carbon dioxide CO2 Calcium in calcium oxide CaO Hydrogen in methane CH4 27% 71% 25% 21/09/2018

Calculating the mass of metal that can be extracted
This rock of iron oxide ore has a mass of 250g. How much iron could be extracted from it? One possible method: 1) Iron oxide has a formula of Fe2O3. Use this information to calculate the percentage masses. 70% iron 2) Use the percentage mass of iron to calculate the mass of iron in the rock. 175g 21/09/2018

Calculating the mass of metal
After you’ve calculated the percentage mass you can work out the actual mass of a metal: Mass of metal = % mass of metal x mass of substance Calculate the mass of metal in the following: Potassium in 10g of potassium chloride, KCl Sodium in 20g of sodium chloride, NaCl Calcium in 50g of calcium chloride, CaCl2 Magnesium in 100g of magnesium chloride, MgCl2 5.2g 7.9g 18g 25.3g 21/09/2018

Solution containing copper and chloride ions
Electrolysis ++++ ---- Positive electrode Negative electrode Cu2+ Cl- Solution containing copper and chloride ions Cu2+ Cl- Cu2+ Cl- 21/09/2018

Electrolysis Electrolysis is used to separate a metal from its compound. = chloride ion = copper ion When we electrolysed copper chloride the _____ chloride ions moved to the ______ electrode and the ______ copper ions moved to the ______ electrode – OPPOSITES ATTRACT!!! 21/09/2018

Words – negative, reactive, move, electrons, molecules, atoms
Extracting Aluminium Aluminium has to be extracted from its ore by electrolysis. This is because aluminium is very ___________. The ore is then melted so that the ions can ______. The positively charged aluminium ions gather at the ___________ electrode where they gain ________ to become neutral atoms. Oxide ions move to the positive electrode where they lose electrons to become oxygen ____ which then combine to form oxygen ________. Words – negative, reactive, move, electrons, molecules, atoms 21/09/2018

Copper, Aluminium and Titanium
21/09/2018 Metal Uses and why Extraction method Problems Copper Electrical wires – good conductor Electrolysis Limited supply Aluminium and titanium Planes – light and corrosion resistant Complicated and expensive Expensive and difficult to extract

21/09/2018 C6a Chemical Synthesis 21/09/2018

Things made by Chemical Synthesis
Paints and pigments Food additives Perfumes and cosmetics Drugs 21/09/2018

Balancing ions Some common ions:
21/09/2018 Balancing ions Some common ions: Sodium – Na+ Potassium – K+ Magnesium – Mg2+ Ammonium – NH4+ Chloride – Cl- Bromide – Br- Oxide – O2- Sulphate – SO42- Determine the formula of these compounds: Sodium chloride Magnesium oxide Magnesium chloride Ammonium chloride Sodium sulphate Sodium oxide Answers: NaCl MgO MgCl2 NH4Cl Na2SO4 NaO 21/09/2018

Simple formulae to learn
H2O CO2 NH3 H2 O2 N2 SO2 Cl2 KCl Water Carbon dioxide Ammonia Hydrogen Oxygen Nitrogen Sulphur dioxide Chlorine Potassium chloride NaCl CaCl2 MgO HCl NaOH Ca(OH)2 CaCO3 HNO3 H2SO4 Mg(OH)2 Sodium chloride Calcium chloride Magnesium oxide Hydrochloric acid Sodium hydroxide Calcium hydroxide Calcium carbonate Nitric acid Sulphuric acid Magnesium hydroxide 21/09/2018

Hazard signs to learn… Acid Corrosive Toxic h i Harmful Irritant
21/09/2018 Hazard signs to learn… Acid Corrosive Toxic h i Harmful Irritant Oxidising 21/09/2018

Common acids and alkalis
Hydrochloric acid, HCl Sodium hydroxide, NaOH Nitric acid, HNO3 Potassium hydroxide, KOH Sulphuric acid, H2SO4 Magnesium hydroxide, Mg(OH)2 Citric acid (a solid) Calcium hydroxide, Ca(OH)2 Ethanoic acid (a liquid) 21/09/2018

The pH scale Strong acid Strong alkali Neutral 1 2 3 4 5 6 7 8 9 10 11
The pH scale is a way of showing how strong or weak an acid or alkali is: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Stomach acid Lemon juice Water Soap Baking powder Oven cleaner Strong alkali Strong acid Neutral An acid contains hydrogen ions, H+ An alkali contains hydroxide ions, OH- 21/09/2018

Different indicators Litmus paper, used to simply indicate if something is acidic or alkaline Universal indicator paper and pH meters, used to detect a pH value 21/09/2018

Sodium + water sodium hydroxide + hydrogen
Balancing equations Consider the following reaction: Sodium + water sodium hydroxide + hydrogen Na O H O H Na + H + This equation doesn’t balance – there are 2 hydrogen atoms on the left hand side (the “reactants” and 3 on the right hand side (the “products”) 21/09/2018

Balancing equations We need to balance the equation:
Sodium + water sodium hydroxide + hydrogen Na O H O H Na O H Na O H + H + Na Now the equation is balanced, and we can write it as: 2Na(s) + 2H2O(l) NaOH(aq) + H2(g) 21/09/2018

Some examples 2 2 3 2 3 Mg + O2 Zn + HCl Fe + Cl2 NaOH + HCl CH4 + O2
Mg O2 Zn HCl Fe Cl2 NaOH HCl CH O2 Ca H2O NaOH H2SO4 CH3OH O2 MgO ZnCl H2 FeCl3 NaCl H2O CO H2O Ca(OH) H2 Na2SO H2O 2 21/09/2018

Words – gold, corroded, fizzes, disappear
Adding acids to metals If an acid is added to a (fairly reactive) metal the metal will be quickly ________ by the acid. We can see a reaction happening because the mixture _________ and the metal eventually __________. Some metals, like ____, are so unreactive that nothing will happen. Words – gold, corroded, fizzes, disappear 21/09/2018

Reactions of metals with acids
When a metal reacts with an acid it gives off hydrogen (which can be “popped” using a lit splint). The other product is a salt. METAL + ACID SALT + HYDROGEN e.g. magnesium + hydrochloric acid magnesium chloride + hydrogen Copy and complete the following reactions: Calcium + hydrochloric acid Zinc + hydrochloric acid Iron + hydrochloric acid Lithium + sulphuric acid 21/09/2018

Adding acid to carbonates
Carbonates are compounds containing carbon and oxygen. When an acid is added to a carbonate the carbonate starts to _______. A gas called ______ _______ is produced. Carbonates used to be used as building materials but aren’t any more because acid rain would eventually ________ the building. Words – dissolve, fizz, carbon dioxide, oxygen 21/09/2018

Reactions of metals carbonates with acid
A metal carbonate is a compound containing a metal, carbon and oxygen. METAL CARBONATE + ACID SALT + CARBON DIOXIDE + WATER Mg H Cl C O Copy and complete the following reactions: Magnesium carbonate + hydrochloric acid Calcium carbonate + hydrochloric acid Sodium carbonate + sulphuric acid 21/09/2018

Reactions of metal oxides with acid
A metal oxide is a compound containing a metal and oxide. They are sometimes called BASES. For example: Mg O Na Al Magnesium oxide Sodium oxide Aluminium oxide METAL OXIDE + ACID SALT + WATER Mg O H Cl Copy and complete the following reactions: Magnesium oxide + hydrochloric acid Calcium oxide + hydrochloric acid Sodium oxide + sulphuric acid 21/09/2018

Neutralisation reactions
A neutralisation reaction occurs when an acid reacts with an alkali. An alkali is a metal oxide or metal hydroxide dissolved in water. ACID + ALKALI SALT + WATER Na Cl H O Copy and complete the following reactions: Sodium hydroxide + hydrochloric acid Calcium hydroxide + hydrochloric acid Sodium hydroxide + sulphuric acid Magnesium hydroxide + sulphuric acid 21/09/2018

Acids and Alkalis 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Acids produce hydrogen ions when they dissolve in water: H Cl + - Alkalis produce hydroxide ions: H O Na - + 21/09/2018

When acids and alkalis react together they will NEUTRALISE each other: Sodium hydroxide Hydrochloric acid Na H OH Cl The sodium “replaces” the hydrogen from HCl Cl Na Sodium chloride H2O Water General equation: H+(aq) + OH-(aq) H2O(l) 21/09/2018

Neutralisation experiment
For example, in a neutralisation experiment we can mix sodium hydroxide (an _____) and hydrochloric acid together and they will ________ each other. The equation for this reaction is… Sodium hydroxide + hydrochloric acid sodium chloride + water A ____ was formed during the reaction, and we could have separated this by __________ the solution. The salt that we formed depended on the acid: Hydrochloric acid will make a CHLORIDE Nitric acid will make a _________ Sulphuric acid will make a _________ Words – nitrate, neutralise, alkali, sulphate, salt, evaporating 21/09/2018

The basic equation for any neutralisation reaction is: H+(aq) + OH-(aq) H2O(l) Write word and chemical equations for the following reactions: Hydrochloric acid + sodium hydroxide Hydrochloric acid + potassium hydroxide Nitric acid + potassium hydroxide Sulphuric acid + calcium hydroxide Nitric acid + copper oxide, CuO Sulphuric acid + calcium carbonate, Ca(CO)3 21/09/2018

Making salts Whenever an acid and alkali neutralise each other we are left with a salt, like a chloride or a sulphate. Complete the following table: Hydrochloric acid Sulphuric acid Nitric acid Sodium hydroxide Sodium chloride (NaCl) + water Potassium hydroxide Potassium sulphate (K2SO4) + water Calcium hydroxide Calcium nitrate (Ca(NO3)2) + water 21/09/2018

Titration 1) Fill a burette with sodium hydroxide solution of known concentration 2) Accurately measure out 25cm3 of acid and place it in the conical flask 3) Add phenolphthalein indicator to the flask 4) Slowly add the alkali until the mixture in the flask turns pink 5) Repeat until you get similar results 21/09/2018

No. of moles = concentration x volume
Titration Equations Q. 0.05dm3 of HCl neutralises 0.1dm3 of NaOH of concentration 0.5mol dm-3. What is the concentration of the acid? The key steps: 1) Look at the equation to compare the numbers of moles: HCl + NaOH NaCl + H2O Notice that 1 mole of HCl neutralises 1 mole of NaOH 2) Use this equation: No. of moles = concentration x volume So, the number of moles of NaOH is (0.5 x 0.1) = 0.05mol According to the equation, this will neutralise 0.05mol of HCl Therefore we have (0.05mol/0.05dm3) = 1mol dm-3 HCl 21/09/2018

Titration Equations 0.2dm3 of HCl neutralises 0.1dm3 of NaOH of concentration 0.5mol dm-3. What is the concentration of the acid? H2SO4 of concentration 0.4mol dm-3 neutralises 0.1dm3 of NaOH of concentration 0.2mol dm-3. How much acid was used? HCl + NaOH NaCl + H2O H2SO4 + 2NaOH Na2SO4 + 2H2O 21/09/2018

21/09/2018 C6b Chemical Synthesis 21/09/2018

Endothermic and exothermic reactions
21/09/2018 Endothermic and exothermic reactions Step 1: Energy must be SUPPLIED to break bonds: Energy Step 2: Energy is RELEASED when new bonds are made: Energy A reaction is EXOTHERMIC if more energy is RELEASED then SUPPLIED. If more energy is SUPPLIED then is RELEASED then the reaction is ENDOTHERMIC 21/09/2018

Common examples of these reactions
Photosynthesis Are these reactions exothermic or endothermic? Burning Hand warmer packs Cooling packs 21/09/2018

Energy level diagrams Energy level
21/09/2018 Energy level diagrams Energy level Energy required to break bonds (endothermic) Energy given out making bonds (exothermic) Reaction progress 21/09/2018

Exothermic vs endothermic:
21/09/2018 Exothermic vs endothermic: What sort of things would industrial chemists need to consider when carrying out large scale exothermic and endothermic reactions? EXOTHERMIC – more energy is given out than is taken in (e.g. burning, respiration) ENDOTHERMIC – energy is taken in but not necessarily given out (e.g. photosynthesis) 21/09/2018

Chemical Synthesis In the manufacture of an inorganic compound the following stages can be used: Work out the reactions that need to be done Carry out a risk assessment Calculate the quantities of reactants to use Do the reaction Separate the product from the mixture Purify it Measure the yield Check its purity 21/09/2018

Different Techniques What would you use these techniques for?
Filtration Dissolving Drying in an oven Evaporation/crystallisation 21/09/2018

Calculating the mass of a product
E.g. what mass of magnesium oxide is produced when 60g of magnesium is burned in air? IGNORE the oxygen in step 2 – the question doesn’t ask for it Step 1: READ the equation: 2Mg + O MgO Step 2: WORK OUT the relative formula masses (Mr): 2Mg = 2 x 24 = MgO = 2 x (24+16) = 80 Step 3: LEARN and APPLY the following 3 points: 48g of Mg makes 80g of MgO 1g of Mg makes 80/48 = 1.66g of MgO 60g of Mg makes 1.66 x 60 = 100g of MgO 21/09/2018

Mr: 2Al2O3 = 2x((2x27)+(3x16)) = 204 4Al = 4x27 = 108
When water is electrolysed it breaks down into hydrogen and oxygen: 2H2O H2 + O2 What mass of hydrogen is produced by the electrolysis of 6g of water? Work out Mr: 2H2O = 2 x ((2x1)+16) = H2 = 2x2 = 4 36g of water produces 4g of hydrogen So 1g of water produces 4/36 = 0.11g of hydrogen 6g of water will produce (4/36) x 6 = 0.66g of hydrogen 2) What mass of calcium oxide is produced when 10g of calcium burns? 2Ca + O CaO Mr: 2Ca = 2x40 = CaO = 2 x (40+16) = 112 80g produces 112g so 10g produces (112/80) x 10 = 14g of CaO 3) What mass of aluminium is produced from 100g of aluminium oxide? 2Al2O Al + 3O2 Mr: 2Al2O3 = 2x((2x27)+(3x16)) = Al = 4x27 = 108 204g produces 108g so 100g produces (108/204) x 100 = 52.9g of Al2O3 21/09/2018

So mass of product = (4/36) x 6g = 0.66g of hydrogen
Another method Try using this equation: Mass of product IN GRAMMES Mass of reactant IN GRAMMES Mr of product Mr of reactant Q. When water is electrolysed it breaks down into hydrogen and oxygen: 2H2O H2 + O2 What mass of hydrogen is produced by the electrolysis of 6g of water? Mass of product IN GRAMMES 4 6g 36 So mass of product = (4/36) x 6g = 0.66g of hydrogen 21/09/2018

The theoretical yield is 136g (using Cl = 35.5) so the % yield is 75%
Percentage Yield Theoretical yield = the amount of product that should be made as calculated from the masses of atoms Actual yield = what was actually produced in a reaction Percentage yield = actual yield (in g) theoretical yield Example question: 65g of zinc reacts with 73g of hydrochloric acid and produces 102g of zinc chloride. What is the percentage yield? Zn + 2HCl ZnCl2 + H2 The theoretical yield is 136g (using Cl = 35.5) so the % yield is 75% 21/09/2018

Percentage yield Percentage yield = Actual yield Predicted yield
X 100% Some example questions: The predicted yield of an experiment to make salt was 10g. If 7g was made what is the percentage yield? Dave is trying to make water. If he predicts to make 15g but only makes 2g what is the percentage yield? Sarah performs an experiment and has a percentage yield of 33%. If she made 50g what was she predicted to make? 70% 13% 150g 21/09/2018

Measuring the Rate of Reaction
Three common methods: 21/09/2018

Rate of reaction graph Amount of product formed/ reactant used up
Slower rate of reaction here due to reactants being used up Fast rate of reaction here Slower reaction Time 21/09/2018

Q. What if less reactants were used?
Rate of reaction graph Q. What if less reactants were used? Amount of product formed/ reactant used up 21/09/2018 Time

Rates of Reaction Oh no! Here comes another one and it’s got more energy… Here comes another one. Look at how slow it’s going… No effect! It didn’t have enough energy! Hi. I’m Mike Marble. I’m about to have some acid poured onto me. Let’s see what happens… It missed! Here comes an acid particle… 21/09/2018

Words – energy, quicker, catalyst, temperature, collide
Rates of Reaction Chemical reactions occur when different atoms or molecules _____ with each other but they HAVE to collide with enough _______. Basically, the more collisions we get and the more energetic they are the _______ the reaction goes. The rate at which the reaction happens depends on four things: The _______ of the reactants, Their concentration Their surface area Whether or not a _______ has been used Words – energy, quicker, catalyst, temperature, collide 21/09/2018

Words – different, speed up, used up, cheaper
Catalyst Summary Catalysts are used to ____ __ a reaction to increase the rate at which a product is made or to make a process ________. They are not normally ___ __ in a reaction and they are reaction-specific (i.e. different reactions need _________ catalysts). Words – different, speed up, used up, cheaper 21/09/2018

Chemical Economics Hi. We’re industrial scientists and we want to make lots of chemicals and sell them to make money. What problems would we face? Possible problems with making chemicals: Reactions often produce chemicals that aren’t commercially useful or that can’t be sold Reactions also need to be fast to be economical but not so fast that they’re dangerous! Therefore we need reactions and processes that give us a pure, high percentage yield where all of the products are useful and the reactions happen quickly. 21/09/2018

OCR Additional Science C4a Chemical Patterns

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OCR Additional Science C4a Chemical Patterns

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