Unit 1 - Chemical Changes and Structure

Reaction Rates

Reaction Rates During the course of a chemical reaction, reactants are being converted into products. Measurement of the rate of reaction involves measuring the ‘change in the amount’ of a reactant or product in a certain time. The rate of reaction changes as it progresses, being relatively fast at the start and slowing towards the end. What is being measured is the average rate over the time interval chosen. Reactions can be followed by measuring changes in concentration, mass and volume.

Where property = mass/volume/concentration Nat 5 Where property = mass/volume/concentration The above is used when there is no change in mass/volume/concentration measured, for example during a colour change reaction. Higher

Calculate the reaction rate; During the first 5 seconds Time (s) Volume (cm3) 0.00 5 7.00 10 10.50 15 12.00 20 12.75 25 13.00 30 Calculate the reaction rate; During the first 5 seconds Between 10-15 seconds Between 20-30 seconds Of the whole reaction (7-0/5-0 = 7/5 = 1.4cm3/s) (12-10.5/15-10 = 1.5/5 = 0.3cm3/s) (13-12.75/30-20 = 0.25/10 = 0.025cm3/s) (13-0/30-0 = 13/30 = 0.43cm3/s)

Collision Theory A chemical reaction can only occur if there is a successful collision between reactant molecules. From S3 we know that we can speed up a chemical reaction by; Decreasing particle size (increasing surface area) Increasing concentration (of reactant) Increasing temperature Adding a catalyst

Collision Theory – Particle Size The smaller the particle size, the higher the surface area. The higher the surface area, the greater the number of collisions that can occur at any one time. The greater the number of collisions, the faster the reaction. Therefore the smaller the particle size, the faster the reaction rate.

Collision Theory – Concentration The higher the concentration, the higher the number of particles. The higher the number of particles, the greater the chance of collisions that can occur. The greater the number of collisions, the faster the reaction. Therefore the higher the concentration, the faster the reaction rate.

Collision Theory – Temperature The higher the temperature, the higher the energy the particles have. The higher the energy, the faster the particles move. The faster the particles move, the greater the chance that they can collide The greater the number of collisions, the faster the reaction. Therefore the higher the temperature, the faster the reaction rate.

Catalysts A catalyst speeds up a chemical reaction without getting used up or changed itself. Catalytic converters are used in exhaust systems to turn harmful gases into less harmful gases. Platinum, rhodium (expensive transition metals) are used as the catalyst used in catalytic converters. https://www.youtube.com/watch?v=rmtFp-SV0tY

Atomic Structure and Bonding

Modern Day Model of the atom The atom is made up of a dense centre called the nucleus, which contains protons and neutrons Modern Day Model of the atom The electrons are very light and are found in a space around the nucleus called the electron shell.

Particle Mass Charge Location Proton Neutron Electron 1 +ve (positive) Neutron (no charge) Electron zero (1/1850) -ve (negative)

Mass Number 16 O Symbol 8 Atomic Number

Important protons electrons neutrons protons atomic number Atomic Number = No. of ____________ No. of Protons = No. of ____________ (when the atom is neutral!) Mass Number = No. of __________ + No. of _________ No. of Neutrons = Mass Number - ____________ __________ protons electrons neutrons protons atomic number

No. Of Protons No. Of Neutrons Atomic Number Mass Number Symbol No. Of Protons No. Of Neutrons Atomic Number Mass Number No. Of Electrons 24 12 Mg 12 80 35 Br 45 40 19 K 19 9 F 9

No. Of Protons No. Of Neutrons Atomic Number Mass Number Symbol No. Of Protons No. Of Neutrons Atomic Number Mass Number No. Of Electrons 16 8 O 31 15 P 24 12 S

What if the element isn’t neutral? Symbol No. Of Protons No. Of Neutrons Atomic Number Mass Number No. Of Electrons 24 12 Mg 2+ 80 35 Br - 40 19 K + 16 8 O 2- when there is a charge the no of protons and electrons are no longer equal. (i.e. the no of electrons change)

Isotopes Protons Electrons Neutrons 28 14 Si 25 31 63 29 Cu 65

Many elements exist as 2 or more isotopes. Isotopes are atoms of the same element (same number of protons) but have different number of neutrons. This means for isotopes, the atomic number stays the same but the mass number changes. Many elements exist as 2 or more isotopes.

relative atomic mass The relative atomic mass (R.A.M.) of an element is the average mass number for a sample of that element. R.A.M is related to isotopes.

example from whiteboard (think number line) 63 65 Cu Cu 29 29 The relative atomic mass of Copper (Cu) is 63.5 What does this tell you about the proportion of the two types of isotopes in a sample of copper? example from whiteboard (think number line)

Electron Arrangements Electrons are arranged in shells (or energy levels.) Lithium has the electron arrangement 2,1 so there are two electrons in the electron shell closest to the nucleus, and one in the next shell: Li X

The 2,8,8,2 Rule For the first 20 elements (hydrogen to calcium) we follow the 2, 8, 8, 2 rule. A maximum of 2 electrons are allowed in the 1st electron shell, 8 electrons in the second, 8 electrons in the 3rd and 2 electrons in the 4th. Each electron shell must be full before the next one is started.

Coincidence? Maybe. Maybe Not? The number of ______ ________ affect the way that the atom reacts. In other words… Elements with the same number of outer electrons (elements in the same group) have similar chemical properties. electrons outer

Important groups to remember; Group 1 – the alkali metals; all very reactive soft metals. (two examples are ________ and ________) Group 2 – alkaline earth metals; similar to group 1 metals but not as soft or reactive. (two examples are ________ and ________) Group 7 – the halogens; very reactive non-metals. (two examples are ________ and ________) Group 8 – the noble gases; very unreactive non-metals (two examples are ________ and ______) In-between groups 2/3 – transition metals. (two examples are ________ and ________)

Remember to label what each colour represents. solids Remember to label what each colour represents. Colour in all of the solid elements one colour (easiest thing to do is leave them white!) Colour in all of the liquids one colour (Bromine and Mercury) Colour in all of the gases one colour. (elements 1, 7, 8, 9, 17 and all of group 0) liquids gases

Carbon Magnesium Potassium Fluorine Oxygen Nitrogen Beryllium For each of the elements (right) write down the following; Name – Symbol - Atomic number – Mass number - Number of protons – Number of electrons – Number of neutrons – Electron Arrangement – Group number – Metal or non metal – Solid, liquid or gas - Carbon Magnesium Potassium Fluorine Oxygen Nitrogen Beryllium Aluminium Neon Bromine

BONDING

Why do atoms bond? Noble gases have a complete outer electron shell. This arrangement of electrons is very stable and therefore other elements want to be like the noble gases. The number of electrons the element needs to lose or gain to be like the noble gases is called the valency. The atoms of other elements can collide together and combine to achieve the full outer electron shell.

The Covalent Bond step 1 Two atoms get close enough to each other to collide. step 1 O X O X Oxygen with red crosses – 2,6 Oxygen with purple crosses – 2,6

The Covalent Bond step 2 The two atoms are attracted to one another through the positive nucleus of one and the negative electrons of the other. step 2 O X O X

The Covalent Bond step 3 O molecule The two atoms combine and share enough outer electrons for each of them to become stable (full outer shell) step 3 X O Oxzygen with red crosses – 2,8 Oxygen with purple crosses – 2,8 O molecule 2

Important !! A covalent bond is a shared pair of electrons between non-metal atoms. A covalent bond is held by the attraction of the positive nucleus and negative outer electrons of the different atoms.

Representing a Covalent Bond We can represent one shared pair of electrons (covalent bond) by “ ”. Therefore hydrogen bonded to hydrogen would be; This molecule is made up of 2 atoms it is classed as diatomic. Mono- means _______ Di- means ________ Tri- means ________ Tetra- means _______ H

Naming Covalent Compounds If a compound name ends in ‘-ide’ then that compound only contains two elements – e.g. carbon nitride contains carbon and nitrogen only. Sometimes prefixes are used in naming compounds – e.g. silicon dioxide Mono – one Di – two Tri – three Tetra - four

Draw the following covalent elements and compounds using both the lines and the overlapping electron shells (circles.) You only have to draw the outermost shell electrons. Hydrogen Chloride (HCl) Phosphorus Trichloride (PCl3) Water (hydrogen oxide) (H2O) Sulphur Fluoride (SF2) Ammonia (nitrogen trihydride) (NH3) Carbon Dioxide (CO2) *** tricky

Working out formula for covalent compounds symbol valency cross cancel formula

Working out formula Examples Hydrogen Sulphide Hydrogen Chloride Phosphorus Oxide Carbon Sulphide Hydrogen Fluoride Carbon Chloride Silicon Oxide Carbon Hydride Nitrogen Hydride Carbon Nitride symbol valency cross cancel formula

Shapes of Molecules tetrahedral Formula = CH4 Name = Carbon Tetrahydride; Structure is drawn like C H tetrahedral

NH3 H2O HCl pyramidal planar / bent linear

Complete this task on paper – only use jotter as last resort Challenge use a pencil Complete this task on paper – only use jotter as last resort Your challenge is to; Work out the chemical formula Name the compound (use prefixes if necessary) Draw the line drawing + Draw these molecules using the overlapping circles methods Identify the shape of the molecule Selenium and Iodine Hydrogen and Fluorine Carbon and Chlorine Carbon and Hydrogen Nitrogen and Hydrogen Phosphorus and Bromine Carbon and Sulphur Silicon and Oxygen

Properties of Covalent Molecules H Methane molecule (CH4) This is a covalent molecule. Other examples include water (H2O), oxygen (O2) and candle wax (C8H18). Covalent molecules; have low melting and boiling points can be solid, liquid or gas at room temperature. never conduct electricity (in any state)

Covalent Network Substances Some covalent substances do not have individual molecules. Diamond is an example of a covalent network structure. Sand (silicon dioxide) is another example.

This is a diamond structure (carbon atoms only.)

Properties of Covalent Network Covalent networks; have extremely high melting and boiling points. are always solid at room temperature. never conduct electricity graphite is the exception to this rule as although it is a covalent network it will conduct electricity.

Weak intermolecular Bond Strong Covalent Bond (hard to break) Weak intermolecular Bond (easy to break)

Covalent Molecular Vs Covalent Network Although the covalent bonds within covalent molecules are strong, the force of attraction between the molecules are weak. These weak forces of attraction don’t require a lot of energy to break and therefore covalent molecules have low melting/boiling pts. All bonds in a covalent networks are very strong covalent bonds and it takes a lot of energy to break these bonds – i.e. very high melting/boiling points.

Type of covalent substances Molecular Network Melting/Boiling Pts Type of bond broken Strength of bonds broken Low Very high Intermolecular Covalent Weak Very strong

Typical Past Paper Questions - Bonding Which line in the table shows the properties of a covalent molecular compound?

Which of the diagrams (left) show the structure of a diatomic compound? A B C D

Which diagram (left) shows the structure of a covalent network structure? A B C D

Ionic Bonding metal When a __________ atom wants to become stable and bond with a non-metal atom, it gives away or loses electrons. Metals lose electrons to get a full outer shell. These ‘lost’ electrons don’t just disappear – instead; Non metals gain electrons to get a full outer shell.

ion ion An ionic bond is between a metal and non metal. An ionic bond is held together via the attraction between the positive metal ion and the negative non metal ion. http://www.youtube.com/watch?v=QqjcCvzWwww

Ionic compounds don’t form molecules like covalent substances Ionic compounds don’t form molecules like covalent substances. They are arranged in large lattice structures. The ________ metals ions are attracted to the _______ non metals ions. This attraction is very strong making an ionic lattice a strong stable substance – because of this ionic compounds are always solid at room temperature. Ionic compound conduct electricity when molten (melted) and when in solution but NOT as a solid. This is because the ions are free to move. Ionic compounds have high melting points and boiling points normally in the range; 400oC to 1400oC. diagram goes here

Making Ions Examples For each of the following elements; Draw the electron arrangement of the atom. Draw the electron arrangement of the ion. Work out the charge of the ion. Name the noble gas that the ion similar to. a) Aluminium f) Oxygen b) Magnesium g) Chlorine c) Lithium h) Nitrogen d) Calcium i) Sulphur e) Potassium j) Bromine

Example; Beryllium Atom Ion The Beryllium ion (charge ____) has the same electron arrangement as the noble gas _________________.

Atom Ion The ___________ ion (charge ____) has the same electron arrangement as the noble gas _________________.

Working out formulae of Ionic Compounds symbol valency cross cancel formula example from whiteboard

Working out formula with complex ions symbol valency (charge) cross Complex ions are ions which contain more than one element. We can identify complex ions from their names as they end in ‘ite’ or ‘ate’. (the exceptions to this rule are hydroxide and ammonium) Sodium Sulphate symbol valency cross cancel formula (charge) Na (SO42-) 1 2 2 1 Na2 (SO42-)

Lithium Chloride Manganese (III) Chloride Work out the chemical formula for the following ionic compounds… Remember the roman numerals indicate the valency of transition metals. (Be careful some contain complex ions – see data booklet) Lithium Chloride Manganese (III) Chloride Aluminium Oxide Copper (III) Carbonate Beryllium Bromide Rhodium (I) Oxide Calcium Carbide Vanadium (II) Sulphate Iron (II) Oxide Barium Carbonate Copper (III) Iodide Cadmium (II) Hydroxide Zinc (I) Sulphite Ammonium Phosphate Calcium Hydroxide Ammonium Dichromate Sodium Carbonate Zinc (II) Sulphide Lithium Nitrate Hafnium (I) Permanganate Hydrogen Sulphate Aluminium Ethanoate Sodium Carbonate Calcium Sulphate Beryllium Fluoride Palladium (II) Bromide Nickel (III) Iodide Titanium (II) Sulphite Caesium Selenide Barium Chromate Potassium Phosphate Silver (I) Oxide Iron (III) Phosphide 63

example from whiteboard Potassium iodide reacts with lead (II) nitrate to form a yellow solid and a clear solution. The products are thought to be lead (II) iodide and potassium nitrate. Word equation Chemical equation example from whiteboard

example from whiteboard Molten iron is used to join steel railway lines together. Molten iron is produced when aluminium reacts with iron (III) oxide. Another product is thought to be aluminium oxide. Word Equation Chemical Equation example from whiteboard

example from whiteboard Calcium carbonate reacts with hydrogen chloride to form a calcium chloride, water and a gas. The gas was tested and is turned limewater from colourless to milky. Write the chemical equation for the above reaction. example from whiteboard

Balancing Equation Examples Not only do we always have to have the same elements on both sides of a ‘reaction arrow’ but we also need to have the same amounts of them too. In order for this to happen we need to balance the equation. 2 2 H = 2 H = 2 O = 2 O = 1 4 4 2

Balancing Equation Practice H2 + Cl2 HCl Al + Cl2 AlCl3 C3H8 + O2 CO2 + H2O Fe2O3 + CO Fe + CO2 *** NaOH + H2SO4 Na2SO4 + H2O NH3 + O2 NO + H2O *** Mg(OH)2 + HCl MgCl2 + H2O *** *** = tricky Now try the sheet – do not write on it.

Calculations

Formula Mass The formula mass (or gram formula mass - gfm) of a substance is obtained by adding the relative atomic masses of all of the elements in a compound together. In other words, the formula mass is the total mass of a compound. The formula mass has NO units.

example from whiteboard Worked Example 1 Calculate the formula mass of calcium chloride. Formula; Formula Mass; Calcium = Chlorine = (Total) = example from whiteboard

example from whiteboard Worked Example 2 Calculate the formula mass of hydrogen sulphite. Formula; Formula Mass; Hydrogen; Sulphur; Oxygen; (total) example from whiteboard

example from whiteboard Worked Example 3 Calculate the formula mass of magnesium nitrate. Formula; Formula Mass; Magnesium = Nitrogen = Oxygen = (Total) = example from whiteboard

Work out chemical formula and formula mass of... Hydrogen oxide Calcium carbonate Carbon dioxide Lithium phosphate Nitrogen fluoride Hydrogen nitrate Aluminium phosphide Ammonium sulphide Magnesium bromide Gold (I) sulphate Copper (II) iodide Silver (I) ethanoate Zinc (III) oxide Potassium dichromate Iron (II) chloride Nickel (III) chromate Lead (II) nitride Tin (II) oxide Mercury (I) bromide Platinum (II) sulphite

The Mole One mole of a substance is the formula mass but with the units grams. For example; One mole of calcium chloride = 111g One mole of hydrogen sulphite = One mole of magnesium nitrate = use previous examples

Important !!! m n fm m = mass of substance n = no. of moles fm = formula mass Important !!! (grams) m n fm (moles)

Rearranging the equation m n fm mass = no. of mole x formula mass m = n X fm no of mole = mass / formula mass n = m fm formula mass = mass / no of moles fm = m n

Calculate the number of moles in 10.1g of potassium nitrate (KNO3) example from whiteboard m n fm

example from whiteboard 0.75moles of a compound X weighs 14g. Calculate the formula mass of the substance. example from whiteboard m n fm

What mass of sodium carbonate (Na2CO3) is present in 0.5 moles? example from whiteboard m n fm

Questions Calculate the mass of 3 moles of copper (I) bromide. CuBr show all working Calculate the mass of 3 moles of copper (I) bromide. CuBr Calculate the mass of 4 moles of calcium nitrate. Ca(NO3)2 How many moles are there in 4.23g of magnesium carbonate? MgCO3 How many moles are there in 1kg of aluminium chloride? AlCl3 0.75 moles of compound Z weigh 102.35g, calculate the formula mass. 1.25 moles of compound Y weigh 69.40g, calculate the formula mass.

How many moles of each substance in; A – 14g of Nitrogen gas (N2) B – 84.5g of Magnesium carbonate C – 400g of Copper (II) oxide D – 321g of Iron (III) hydroxide What is the mass of; A – 1 mole of aluminium B – 2.5 Moles of Oxygen gas (O2) C – 0.5 moles of Lithium sulphate D – 0.1 moles of ethane (C2H6)

Calculation using Balanced Equation Balanced equations can be used to calculate masses of substances involved in chemical reactions. When we write the balanced chemical equation, the number in front of each formula represents the number of moles of the substance. e.g. Ca + 2HNO3 Ca (NO3)2 + H2

example from whiteboard What mass of calcium chloride would be produced when 10g of calcium reacts fully with hydrogen chloride? Ca + 2HCl CaCl2 + H2 example from whiteboard

CH4 + 2O2 CO2 + 2H2O What mass of carbon dioxide is formed when 64g of methane are burned completely in air?

example from whiteboard Calculate the mass of iron that would be produced from 2 moles of iron (lll) oxide. Fe2O3 + 3H2 2Fe + 3H2O example from whiteboard

example from whiteboard C9H2O + 14 O2 9 CO2 + 10 H2O Calculate the mass of water produced when 6.4g of nonane (C9H2O) is burned. example from whiteboard

Acids and Bases

The pH scale… 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Acids Alkalis Neutral

What does it really mean? Red - very acidic Orange - slightly acidic Yellow - very slightly acidic Green - neutral Green/Blue – very slightly alkaline Blue - slightly alkaline Purple - very alkaline 90

Oxide Acid formed Other name of acid Acid formula Ions in the acid Carbon Dioxide Carbonic Acid Hydrogen Carbonate Sulphur trioxide Sulphuric Acid Hydrogen Sulphate Sulphur dioxide Sulphurous Acid Hydrogen Sulphite Nitrogen Dioxide Nitric Acid Hydrochloric Acid Hydrogen Chloride Ethanoic Acid Hydrogen Ethanoate

What conclusion can you come to..? ALL acids contain H ions

Acids have an excess of hydrogen ions An acid is a solution which has a greater _____________________________ ______________ than pure water. i.e. Acids have an excess of hydrogen ions (H+ ions)

Oxide Name of alkali formed Formula of alkali Ions in the alkali Sodium Oxide Sodium Hydroxide Potassium Oxide Calcium Oxide Ammonia (NH3) Ammonium Hydroxide

What conclusion can you come to..? ALL alkalis contain OH ions

Alkalis have an excess of hydroxide ions (OH- ions) An alkali is a solution which has a greater ______________________________ than pure water. i.e. Alkalis have an excess of hydroxide ions (OH- ions)

equation from white board Neutral Substances equation from white board Water has equal amounts of H+ and OH- ions so the overall pH is neutral (pH 7) During neutralisation reactions the H+ ion (from the acid) and the OH- ion (from the alkali) react and produce water. The H+ and OH- ions being able to move is the reason why water conducts electricity.

Important Summary All solutions contain both H+ and OH- ions. Acids have more H+ than OH- ions Alkalis have more OH- than H+ ions Neutral substances have equal amounts of H+ and OH- ions

Diluting Acids or Alkalis Diluting an acid or alkali is similar to what happens with diluting juice. As an acid is diluted it becomes ‘weaker’ as there are less H+ ions. As a result the pH increases towards pH 7 until it eventually becomes neutral. As an alkali is diluted it becomes ‘weaker’ as there are less OH- ions. This means the pH decreases towards pH 7 (neutral)

Neutralisation Reactions Acids can be neutralised using bases. Worked Example General Equation 1 ACID + Metal Hydroxide SALT + WATER Sodium Hydroxide + Hydrochloric Acid Sodium Chloride + Water

Bases Bases are another word for alkalis. Examples of bases are; metal hydroxides, metal oxides and metal carbonates. Bases neutralise acids to form water.

Salts Salts are _______ _______ compounds (contain a positive and negative charge). We can name the salt produced by looking at the acid and base that have been used. soluble ionic

The first part of the salt’s name comes from the base used; e.g. Sodium Hydroxide gives – sodium ……. Calcium Oxide gives – calcium ……. Ammonia gives – ammonium……. The second part of the name comes from the type of acid used during the neutralisation; Hydrochloric acid produces .......... chloride salts Sulphuric acid produces ................. sulphate salts Nitric acid produces ..................... nitrate salts Ethanoic acid produces ……………… ethanoate salts

questions 1. Complete the names of the salts produced; a) Calcium Hydroxide + Hydrochloric Acid b) Sodium oxide + Nitric Acid c) Potassium carbonate + Sulphuric Acid 2. Which acid has been used to make calcium sulphate? 3. Write the word equation for magnesium hydroxide reacting with an acid of your choice.

Metal Oxide + Acid reaction General Equation ACID + METAL OXIDE SALT + WATER Example (from your experiment) Word Equation Chemical Equation (balance if necessary)

Add 10cm3 of acid and 10cm3 of water to a 100cm3 beaker. Heat the acid until ALMOST boiling using a slightly blue flame. When the acid is hot enough, use a spatula to add small amounts of copper(II) oxide (1g in total) to the beaker. Stir the mixture gently for up to half a minute after each addition. When all the copper(II) oxide has been added, continue to heat gently for 1 to 2min to ensure reaction is finished. Allow the beaker to cool while you set up the filtration.

Metal Carbonate + Acid reactions Calcium carbonate (limestone) is often used for building materials. Metal carbonates react with acid, so acid rain can damage limestone buildings. General Equation ACID + METAL CARBONATE SALT + WATER + CARBON DIOXIDE

_________________ and _________________ questions 1. Complete the names of the salts produced; a) Calcium Hydroxide + Hydrochloric Acid b) Sodium Hydroxide + Nitric Acid c) Potassium Hydroxide + Sulphuric Acid 2. Which acid and alkali can be used to make Calcium Sulphate? _________________ and _________________ 3. Write the word equation for magnesium hydroxide reacting with an acid- you choose the acid.

Ionic Formula Writing ionic formula is simply writing the chemical formula of a compound but showing the charges of the ions. Metals form positive/negative ions Non metals form positive/negative ions. Chemical Formula – NaOH Ionic Formula – Na+ OH-

Spectator Ions When acids and alkalis are added to water, they dissociate to form ions. Some of these ions react, and some do not. The ions that don’t react are called spectator ions. Ionic equations make it easier to identify spectator ions. Rather than write the chemical formula of reactants and products, we can write the ions present in aqueous solution:

Sodium Hydroxide + Hydrochloric Acid Worked Example Word Equation; Formula Equation (with state symbols); Ionic Equation (with state symbols); Spectator ions appear on reactant and product sides of the reaction and remain unchanged, so we can cross them out. Rewrite equation without (omitting) spectator ions

Mole and Solution Calculation For solutions we use a different triangle. This allows us to work out the number of moles of solute (substance dissolved), volume (in litres), or concentration of solution. 1 ml = 1 cm3 1000ml = 1000cm3 1000cm3 = 1 litre 1cm3 = 1/1000 = 0.001 litres 200cm3 = 200/1000 = 0.2 litres useful

Important !!! n c V n = no of moles (moles) c = concentration (mol/l or moll-1) v = volume (litres) Important !!! n c V

Rearranging the equation c V no of moles = concentration x volume n = c X v concentration = no of moles / volume c = n v volume = no of moles / concentration v = n c

example from whiteboard Calculate the no. of moles of potassium hydroxide which must be dissolved to make 200 cm3 0.5 mol/l solution example from whiteboard n c V

example from whiteboard Calculate the concentration of the following solution: 0.1 mole of hydrogen chloride dissolved to make 500 cm3 of solution. example from whiteboard n c V

example from whiteboard Calculate the volume (in litres) of the following solution: 5 mol/l solution containing 2 moles of sodium hydroxide. example from whiteboard n c V

Calculate the mass, in grams, of sulphuric acid (H2SO4) present in 500cm3 of a 5 mol/l solution

Titration Calculation Step 1: Write the formula: (C x V x P)acid = (C x V x P)alkali C = Concentration of acid or alkali V = Volume of acid or alkali – Always make sure the units of volume are the same on each side!! P = Number of H+ (for acid) Number of OH- (for alkali)

Step 2: Find out the number of H+ in the formula of acid. (e.g. HCl= 1 , H2SO4= 2) OR Find out the number of OH- in the formula of alkali. (e.g. NaOH= 1, Mg(OH)2= 2) Step 3: Put all of the known values into the equation shown above. Step 4: Complete the calculation.

Examples of Power Work out the powers of either the H+ (acids) or OH- (alkalis) in the following; NaOH Ca(OH)2 H3PO4 HCl H2SO4 Al(OH)3 H5S2

(C x V x P)acid = (C x V x P)alkali Worked Example In a titration, 10 cm3 of 2 mol/l sodium hydroxide (NaOH) solution was neutralised by 25cm3 of dilute hydrochloric acid (HCl). Calculate the concentration of the acid in mol/l. (C x V x P)acid = (C x V x P)alkali example from whiteboard

example from whiteboard In a titration, 25 cm3 of 2 mol/l sodium hydroxide (NaOH) solution was neutralised by 28.7cm3 of sulphuric acid (H2SO4). Calculate the concentration of the acid in mol/l. example from whiteboard

example from whiteboard In a titration, 20 cm3 of potassium hydroxide (KOH) solution was neutralised by 42.6cm3 of 0.5 mol/l hyrdochloric acid (HCl). Calculate the concentration of the base in mol/l. example from whiteboard

example from whiteboard In a titration, 2 mol/l sodium hydroxide (NaOH) solution was neutralised by 22cm3 of 0.1mol/l sulphuric acid (H2SO4). Calculate the volume of the base in cm3 that was neutralised. example from whiteboard

example from whiteboard In a titration, 0.05 mol/l potassium hydroxide (KOH) solution was neutralised by 17.1cm3 of 0.25mol/l phosphic acid (H3PO4). Calculate the volume of the base in cm3 that was neutralised. example from whiteboard

Never (EVER) use 'rough' values in calculations