2 Stoichiometry is the part of chemistry that studies amounts of substances that are involved in reactions.It could be amounts of substances before the reaction or amount of material that is produced by the reaction.Stoichiometry is all about amounts.
3 What a balanced chemical equation tells us A chemical equation represents the mole ratio of reactants and productsCuCl2 + 2AgNO3 2AgCl + Cu(NO3)21mol mol mol molNaOH + HCl NaCl + H2O1mol mol mol 1mol2CO + O2 -> 2CO22mol mol 2molMg + 2HCl -> MgCl2 + H21 mol 2 mol 1 mol mol
4 Stoichiometry will tell you that if you have ten million atoms of sodium (Na) and only one atom of chlorine (Cl) you can only make one molecule of sodium chloride (NaCl). Nothing you can do will change that. Like this:10,000,000 Na + 1 Cl --> NaCl + 9,999,999 Na
5 Limiting reagent A reagent is another word for reactant A reaction will stop when one reactant is used up before the otherThis is called a limiting reagentThe other reactant is the excess reagentBlue is the limiting reagentRed is the excess reagent
7 Mass-Mass stoichemtry Involves solving a problem in which the mass of a reactant or a product is given
8 Calculating the mass of a substance given the mass of another reactant or product Write a balanced chemical equationIdentify known and unknown quantities of substancesCalculate the number of moles of known quantitiesFind the molar ratio and use this to calculate the number of moles of a required substanceMol of required substance = Molar ratioMol of given substance5. Calculate the quantity o the required, unknown, substance
9 CalculationsCalculate the number of moles of CO2 formed in the combustion of ethane C2H6 in a process when 35.0 mol of O2 is consumed. The reaction is:2 C2H6 + 7 O2 4 CO2 + 6 H2O4 CO2 : 7 O235.0 mol O2 x 4 CO2 mol = 20.0 mol CO27 mol O2 mol
10 Two moles of Mg and five moles of O2 are placed in a reaction vessel, and then the Mg is ignited according to the reaction Mg + O2 MgO.Identify the limiting reagent in this experiment.2 Mg + O2 2 MgO2 mol 1mol (I have 5, 5 -1 = 4 mol unused)Four moles of oxygen will remain unreacted.Oxygen is the excess reagent, and Mg is the limiting reagent.
11 What mass of iron (III) oxide is formed from the complete combustion of 183.5g of pyites (FeS2) FeS2 + O2 Fe2O3 + SO24FeS2 + 11O2 2Fe2O3 + 8SO2molar mass of FeS2 = (2 x 32.1)= g/mol= 183.5g x 1 mol120.05g= mol
12 3. Find the molar ratio of 4FeS2 to 2Fe2O3 4:2 2:1 4:2 2:1Mol of Fe2O3 = 2 FeS2 = 1= mol2Mol of Fe2O3 = mol4. Molar mass of Fe2O3 = 2 x x 16= g/molmol x 159.7g1mol= 122.1g of Fe2O3
13 Calculate the mass of water produced when 2 Calculate the mass of water produced when 2.8g of CH4 is burnt in the airCH4 + 2O2 2H2O + CO2Molar mass = = 16g/molMol of CH4 = 2.8g x 1 mol16gMol of CH4 = mol3. Molar ratioCH4 : H2O 1:2CH4 = 1 = mol = mol of H2OH2O4. Molar mass of H20 = 2+16 = 18g/molMass of H20 = mol x 18g = 1.575g1 mol
14 Limiting reagentHow much precipitate can you make with only 2.6mol of KCl?AgNO3 + KCl AgNO3(aq) + KCl(aq) AgCl (s) + KNO3(aq)2.6molKCL is the limiting reagent we only have a certain amount of it
15 Balance equationAgNO3(aq) + KCl(aq) AgCl (s) + KNO3(aq)Determine molar ratioKCl to AgCl is 1:1I have 2.6mol of KCl I have 2.6 mol of AgClMolar mass of AgCl = g/mol2.6mol KCl x 1mol of AgCl x g of AgCl1 mol of KCL mol of AgCl= g of AgCl
16 If 6.3g of S8 react with Pb, how many grams of PbS are formed? Pb + S8 PbS8Pb + S8 8PbS6.3g ?Molar mass of S8 = x 8 = g/molMol of S8 = 6.6g x 1mol256.48g= molMolar ratio = PbS 8SMol of PbS = 8 x = molMolar mass of PbS = g/molMass of PbS = 1.647mol x g1 mol= g
17 Determine the limiting reagent What mass of liquid water is formed when 2.3g of H2 gas and 4.55g of O2 gas react together2H2 + O2 2H2O2.3g gMolar mass of H2 = 2g/molMol of H2 = 2.3g x 1mol = 1.15mol2gMolar mass of 02 = 32g/molMol of O2 = 4.55 x 1 mol = 0.142mol32g
18 2H2 + O2 2H2O x 2 = 0.284mol of H2 Which is the limiting reagent? 02 2H2 + O2 2H2O Molar mass of H2O = 18g/mol Mass of H2O = 0.282mol x 18g 1 mol = 5.076g
19 What volume of 0. 100mol/L H2SO4 acid reacts completely with 17 What volume of 0.100mol/L H2SO4 acid reacts completely with 17.8mL of 0.15 of potassium hydroxide?Molar ratio = H2SO4 1KOHMol of H2SO4 = ½ x molL of H2SO4 = mol x 1L0.1molL of H2SO4 = LAcid + base salt + waterKOH H2SO4 K2SO4 + H202KOH H2SO4 K2SO4 + 2H200.15M M17.8mL ?(0.0178L)Mol of KOH = L x 0.15mol1L= mol
20 Zinc metal is reacted with 400mL of a 0 Zinc metal is reacted with 400mL of a 0.25mol/L solution of sulfuric acid. Calculate the mass of zinc sulfate formed
22 TitrationA titration is a method of analysis that will allow you to determine the precise endpoint of a reaction and therefore the precise quantity of reactant in the titration flask. A buret is used to deliver the second reactant to the flask and an indicator or pH Meter is used to detect the endpoint of the reaction.
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