2 DO-NOW – Silent and Independent! Remember:(g) = gas (l) = liquid (s) = solid(aq) = aqueousMust use rules for naming/writing formulasIonic compounds – balance charges, NO prefixesCovalent compounds – use prefixes
3 Information from Chemical Equations To produce fertilizers, Nitrogen gas is combined with Hydrogen gas to produce Nitrogen trihydride (ammonia).N2(g) + H2(g) NH3(g)
4 Information from Chemical Equations Making fertilizer uses a lot of energy and a lot of raw materialsEfficiency is key!!How can knowledge aboutchemical reactions makeThis process as efficientas possible?
5 The Law of Conservation of Mass In a chemical reaction, matter is never created or destroyed.The number of atoms and the mass of the reactants must be equal to the number of atoms and the mass of the products.
6 Mini-Lab! NaHCO3(s) + CH3COOH(aq) CO2(g) + H2O(l) + NaCO3(aq) Baking soda reacts with acetic acid (vinegar) to produce…Carbon dioxide gas, liquid water, and sodium carbonate solutionInitial mass:Final mass:
7 Mini - Lab Find the mass of both reagents IN THEIR CONTAINERS. Record this mass as your initial massRemove materials from balanceCarefully pour the acetic acid into the baking soda. Agitate until bubbling stopsFind the mass of both reagents IN THEIR CONTAINERS again.Record this mass as your final mass
8 What were your results?Thoughts? Why doesn’t this reaction seem to obey the law of conservation of mass?What could we do to confirm that it satisfies the law of conservation of mass?
9 More examples: Law of Conservation of Mass CS2(l) + O2(g) CO2(g) + SO2(g)If I reacted 5 grams of CS2 with 5 grams of O2, and the reaction produced 2 grams of CO2, how many grams of SO2 must have been produced?If my products had a total mass of 20 grams, how many grams of reactants must I have started with?If I reacted 3 grams of CS2 with an unknown number of grams of O2 and produced a total of 4 grams of products, what was the mass of the O2?
10 Balancing Chemical Equations How do we show, in a chemical equation, that the law of conservation of mass is being obeyed?The law of conservation of mass must be satisfied by equalizing the number of atoms on the reactant and the product sides.Use coefficients to show how many molecules of each compound.
12 Rules for balancing an equation 1. Only change the coefficients that appear in front of an element or compound2. Never change any subscripts in a formula3. Coefficients should be written as the lowest possible ratios4. Begin by balancing elements that appear ONLY once on each side of the equation
23 Building a TricycleTo build a tricycle, you need a frame, a seat, 3 wheels, a set of handlebars and 2 pedalsIf I wanted to build 2 tricycles,How many seats would I need?How many wheels?What if I wanted 346 tricycles?
24 Balanced Chemical Equations Chemical equations are our recipes for chemical reactions!Balanced chemical equations can be used to calculate how much reactant we will use or how much product is formed from a chemical reaction
25 Coefficients indicate relative numbers of moles or molecules of reactants and products. H2(g) + Cl2(g) 2HCl(g)One mole of hydrogen reacts with one mole of chlorine gas to yield two moles of hydrogen chloride gas. OR:One molecule of hydrogen gas reacts with one molecule of chlorine gas to yield two molecules of hydrogen chloride gas.
26 N2(g) +3H2(g) 2NH3(g) Number of Molecules – look at coefficients: 1 molecule of N23 molecules of H22 molecules of NH3Just like with atoms, it makes more practical sense to use Avogadro's number (1 mole) of molecules rather than individual molecules
27 N2(g) +3H2(g) 2NH3(g) Number of Moles – look at coefficients: 1 mole of N23 moles of H22 moles of NH3Note that the number of moles (like the number of molecules) is not the same on both sides!
28 Na2O(s) + 2CO2(g) + H2O(g) 2NaHCO3(s) How many moles of sodium oxide?How many moles of carbon dioxide?How many moles of water vapor?How many moles of sodium hydrogen carbonate?
30 Mole RatiosWhat is the RATIO between tricycle seats and tricycle wheels?1 seat : 3 wheels1 seat3 wheelsUsing the fractional form of the ratio is going to make a lot more sense in chemistry
31 Mole Ratios N2(g) +3H2(g) 2NH3(g) What are the mole ratios between: moles of N2 and moles of H2?moles of NH3 and moles of N2?moles of H2 and moles of NH3?1mol N mol NH mol H23mol H mol N mol NH3
32 2H2O(l) 2H2(g) + O2(g) How many moles of water? How many moles of oxygen gas?How many moles of hydrogen gas?Mole ratio of water to hydrogen gas.Mole ratio of oxygen gas to hydrogen gas.
33 CS2(l) + 3O2(g) CO2(g) + 2SO2(g) How many moles of oxygen gas?How many moles of carbon dioxide gas?Mole ratio of oxygen to carbon dioxide.Mole ratio of carbon disulfide to oxygen.Mole ratio of carbon dioxide to sulfur dioxide.
34 4Fe(s) + 3O2(g) 2Fe2O3(s) Mole ratio of iron to oxygen gas. Mole ratio of oxygen gas to iron (III) oxide.Mole ratio of iron (III) oxide to iron.
36 N2(g) +3H2(g) 2NH3(g)How many moles of ammonia will I get by reacting 2 moles of nitrogen gas?2mol N2 x 2 mol NH3 = 4 mol NH3mol N2The ONLY way to relate amounts of two different substances is to use the MOLE RATIO!!GIVENMOLE RATIO
37 MOLE MOLE conversions To get from moles of substance A to moles of substance B, always use the mole ratio!STEP 1: Write the given value (with a unit) over 1STEP 2: Write a blank conversion factorSTEP 3: Fill in the units to cancel your given unitSTEP 4: Complete the mole ratioSTEP 5: Multiply/Divide to get final answer
38 How many moles of nitrogen gas react with 12 moles of hydrogen gas? N2(g) +3H2(g) 2NH3(g)How many moles of nitrogen gas react with 12 moles of hydrogen gas?12 mol H2 x 1 mol N2 = 4 mol N2mol H2The ONLY way to relate amounts of two different substances is to use the MOLE RATIO!!GIVENMOLE RATIO
39 4Fe(s) + 3O2(g) 2Fe2O3(s)How many moles of oxygen gas react with 4 moles of solid iron?How many moles of iron (III) oxide are produced by the reaction of 3 moles of oxygen gas?How many moles of solid iron are required to react with 3 moles of oxygen gas?How many molecules of iron (III) oxide are produced by the reaction of 4 molecules of solid iron?
40 CS2(l) + 3O2(g) CO2(g) + 2SO2(g) How many molecules of CS2 react with 9 molecules of O2?How many molecules of O2 react with 2 molecules of CS2?How many moles of CO2 are produced by the reaction of 3 moles of CS2?How many moles of SO2 are produced by the reaction of 12 moles of O2?