Unit 6: Chemical Reactions

What is a chemical reaction? One or more substances change into one or more new substances whose chemical and physical properties differ from the original substances Find a video clip to do after this

Signs of a Chemical Reaction

Chemical Reaction or Not?

Reading Chemical Equations Chemical equation: shows the chemical formulas and the relative amounts of all reactants and products separated by an arrow CH4 + O2  H20 + CO2 Products Reactants

What is all the symbolism? Meaning of the arrows " " symbol is used to denote a net forward reaction. " " symbol is used to denote a reaction in both directions. " " symbol is used to denote an equilibrium. Nature of the substrates aq = aqueous l = liquid s = solid g = gas

Decoding Equations: What do the following equations mean? H2CO3(aq)  →   H2O(l) + CO2(g) Aqueous carbonic acid yields water and carbon dioxide gas NH4OH(aq)  →   NH3(g) + H2O(l) Aqueous ammonium hydroxide yields ammonia gas + water

What is all the symbolism? More arrows with special features

Classifying chemical reactions Classifying chemical reactions allows us to be able to predict the products when only given the reactants There are 5 main ones: Combustion Synthesis Decomposition Single displacement Double-displacement

Types of Chemical Reactions Combustion: the reaction of a carbon-based compound with oxygen Carbon based compound + oxygen  carbon dioxide + water i.e. CH4 + O2  H20 + CO2 What’s a fire and why does it… what’s the word? Burn…

Types of Chemical Reactions 2. Synthesis: a single compound forms two or more reactants A + B  AB i.e. C + O2  CO2 i.e. CaO + H2O  Ca(OH)2

Types of Reactions Decomposition: a single compound breaks down into two or more elements or simpler compounds AB  A + B i.e. 2H2O (l)  2H2 (g) + O2 (g)

Types of Reactions Displacement Single Displacement: a single element reacts with a compound and displaces another element from the compound A + BC  B + AC i.e. 2Al (s) + 3CuCl2 (aq)  2AlCl3 (aq) + 3Cu (s) Double Displacement: two compounds appear to exchange ions and form new compounds AB + CD  AD + CB i.e. HCl (aq) + NaOH (aq)  HOH (l) + NaCl (aq)

Practice: which type of reaction does each chemical equation represent? Ca(OH)2 + Al2(SO4)3  CaSO4 + Al(OH)3 Mg + Fe2O3  Fe + MgO C2H4 + O2  CO2 + H2O PbSO4  PbSO3 + O2 NH3 + I2  N2I6 + H2 H2O + SO3  H2SO4 HW: finish Have a WS where they have to figure out which equation is which Next day, do a lesson on determining the products given that it is a certain kind of reaction

Predicting the Products of Single Displacement Reactions Elements will only displace an element that is less reactive than itself To determine which elements are most reactive, chemists use an activity series

Practice Will magnesium react with lead (II) nitrate? Write out the chemical equation Mg + Pb(NO3)2  Identify the reactants Will Mg displace Pb? 3. Check the activity series Mg is above Pb ergo the rxn will take place Write the products Mg + Pb(NO3)2  Pb + Mg(NO3)2

More practice Will copper react with lead (II) nitrate? Write out the chemical equation Cu + Pb(NO3)2  Identify the reactants Will Cu displace Pb? 3. Check the activity series Cu is below Pb ergo the rxn WILL NOT TAKE PLACE Write the products Mg + Pb(NO3)2  No reaction

Predicting whether or not chemicals will react in displacement reactions In order for a double displacement to occur, one of the products must be a solid precipitate, a gas, or a molecular compound We will be focusing on precipitation reactions, and predicting whether or not there will be a precipitate. Then show an example of a precipitation rxn

Precipitation Reaction In order for a precipitation reaction to occur, at least one of the products must be a solid (precipitate) Therefore, we use solubility rules to determine what is soluble in water (aq) and what is not (s).

Compounds containing these ions are soluble in water: Group 1A elements (Li, Na, K, Rb, Cs, Fr) Exceptions: LiF Ammonium salts (NH4+) Exceptions: none Nitrate (NO3-), chlorate (ClO3-), and perchlorate (ClO4-) Acetate (CH3COO- or C2H3O2-, sometimes abbreviated as Oac-) Exceptions: Fe3+ Chlorides (Cl-), bromides (Br-), and iodides (I-) Exceptions: Ag+, Pb2+, and Hg22+ Sulfate ( SO42-) Exceptions: Ba2+, Sr2+, Ca2+, Pb2+, Hg22+, and Hg2+, Ca2+ and Ag+ Compounds containing these ions are insoluble in water Hydroxide (OH-) Exceptions: Group IA (alkali metals), Ba2+, Ca2+, and Sr2+. Sulfide (S2-) Exceptions: Groups I-A and II-A (alkali metals and alkali earth metals) Sulfites (SO32-), carbonates (CO32-), chromates (CrO42-), and phosphates (PO43-) Exceptions: NH4+ and Group I-A (alkali metals) Oxides (O2-) Exceptions: Group 1, Ca2+, Sr2+, and Ba2+

Group Work Groups Group 1 Alameen Gulberlyne Shaquo Group 4 Ruvym Klea Brandon Group 7 Gheed Gabi Son Group 10 Laura Kim Marcus Group 8 Esther Edward Deana Brandy Group 2 Calvin Riya Pascal Brandy Group 5 Justine Jeneiva Huy Trieu Group 9 Daniela Daisha Ciera Will Group 3 Pam Niyati Asmar Group 6 Huy To Huiwen Firuza

Example Will ammonium carbonate react with magnesium chloride? Write out the chemical equation (NH4)2CO3 (l)+ MgCl2 (l) ??? Figure out the products (NH4)2CO3 (l)+ MgCl2 (l) NH4Cl + MgCO3 Figure out the solubility of the products using the solubility rules NH4Cl is soluble because all compounds with ammonium in them are soluble MgCO3 is insoluble because all (almost) all compounds with CO3 in them are insoluble 4. Determine whether the reaction takes place YES!

Another example Will iron (III) nitrate react with magnesium acetate? Write out the chemical equation Fe(NO3)3 + Mg(C2H3O2)2 ??? Figure out the products Fe(NO3)3 + Mg(C2H3O2)2 Fe (C2H3O2)3 + Mg(NO3)2 Figure out the solubility of the products using the solubility rules Mg(NO3)2 is soluble because all compounds with nitrate in them are soluble Fe (C2H3O2)3 is insoluble because though (almost) all compounds with C2H3O2 in them are soluble, it is insoluble when its bonded with Fe (the exception) 4. Determine whether the reaction takes place YES!

Homework Problem Review lithium carbonate + chromium (III) nitrate →

Homework Problem Review Na3PO4 + Ba(NO3)2 →

Homework Problem Review AgBr + BaI2 →

Homework Problem Review silver chlorate + potassium chloride →

Homework Problem Review lead (II) chlorate + magnesium chloride →