2. The percent yield is the maximum amount of product that can be produced from the given amount of limiting reactant.

Transcription

1 UNIT 6 stoichiometry practice test True/False Indicate whether the statement is true or false. moles F 1. The mole ratio is a comparison of how many grams of one substance are required to participate in a chemical reaction with another substance, based on an unbalanced chemical equation. Balanced F T F 2. The percent yield is the maximum amount of product that can be produced from the given amount of limiting reactant. Theoretical yield 3. Stoichiometry is the study of the relationship between the amount of reactants used and the amount of products made in a chemical reaction. 4. In a chemical reaction, the reactant that is completely used up is called the excess reactant. Limiting F 5. A mole ratio from balanced equation below is 3 mole H2 : 1 mole HCl 3moleH2 : 6 mole HCl 2Al + 6HCl 2 AlCl3 + 3H2 Multiple choice choose the best answer 6. What is the density of Ne (hint Ne is NOT diatomic) STP? molar mass divided by 22.4L a) 452g/L b ) 1.11 g/l c) 1.80 g/l d) g/l 7. Which of these expressions is an incorrect interpretation of the balanced equation? 2S(s) + 3O2(g) 2SO3(g) a. YES 2 atoms S + 3 molecules O2 2 molecules SO3 c. YES 2 mole S + 3 mole O2 2 mole SO3 b. NO 2 grams S + 3 grams O2 2 grams SO3 d. none of these 8. Which mole ratio is needed to determine how many moles of P react with 332 moles Ca? bal eq is 3 Ca + 2 P 1 Ca3P2 a) 3 mol P b) 2 mole P c) 2 mole Ca d) 1 mole Ca3P2 2 mole Ca 3 mole Ca 3 mole P 5 mole Ca

2 9. Nitrogen oxide is oxidized in air to give brown nitrogen dioxide. 2 NO(g) + O2(g) 2 NO2(g) If you have 2.2 moles of O2, (A) you need 2.2 moles of NO for a complete reaction and you will produce 2.2 moles of NO 2. (B) you need 1.1 moles of NO for a complete reaction and you will produce 4.4 moles of NO 2. (C) you need 1.1 moles of NO for a complete reaction and you will produce 3.3 moles of NO 2. (D) you need 4.4 moles of NO for a complete reaction and you will produce 4.4 moles of NO 2. (E) you need 4.4 moles of NO for a complete reaction and you will produce 2.2 moles of NO 2. B 10. How many moles of Cu are needed to react with 12.6 moles of AgNO 3? Bal eq is Cu + 2 AgNO 3 2 Ag + Cu(NO 3 ) 2 a moles b. 6.3 moles c moles d. 4.3 moles 12.6 moles AgNO 3 1 mole Cu 2 mole AgNO If 492 grams of KClO3 were heated in a test tube, how many grams of oxygen gas should be given off? Bal eq is 2 KClO3 2 KCl + 3 O2 ( KClO3 123 g/mol) a. 192 g b g c g d. 322g 492 grams of KClO3 1 mole KClO3 3 mole O grams O2 123 g KClO3 2 mole KClO3 1 mole O2 STP how many liters of CO2 are produced when 4.00 liters C3H8 react with excess O2 based on the combustion of propane? Bal eq is 1 C3H8 + 5 O2 3 CO2 + 4 H2O a) 12.0 liters CO2 b) 4.00 liters CO2 c) 269 liter CO2 d) 6.02x liters CO liters C3H8 5 liter CO 2 1 liter C3H8

3 13. Calculate the volume ( Liters) of H2 gas needed to react with when 84.0 grams N2 STP Bal eq is N2 + 3H2 2 NH3 a Liters b. 202 Liters c Liters d Liters 14 Given the Balanced equation 1 Fe + 2 HCl FeCl2 + H2 this is a 1 Fe : 2HCl What is the limiting reactant when 18 moles Fe react with 3 moles HCl during an experiment? According to balanced equation 18 moles Fe needs 9 moles HCl ONLY have 3 moles HCl Which is NOT ENOUGH Which means HCl limits production a) FeCl2 b) H2 c) Fe d) HCl 15. % yield is the quantity of product actually produced in lab compared with the quantity of a. Product expected c) The excess reactant b. The limiting reactant d) The reactants plus the product 16. A chemical reaction can theoretically produce grams of product, but in actuality grams are produced. Which is the percent yield for this reaction? a. 82.1% b % c. 24.6% d. 17.9% 17. How much heat is involved when 8.00 g of H2 is reacted according to the following equation: Thermochemical equation is N2 + 3H2 2 NH3 H -56 kj A. 112 kj B. 672 kj C kj D kj 8.00 g of H2 1 mole H2 56 kj 2.00 g H2 3 mole H2

4 Free Response 1) Given this balanced equation 2 C2H6 + 7 O2 4 CO2 + 6 H2O How many grams of C 2 H 6 gas are required to produce 728 grams of water? 728 grams H 2 O 1 mole H 2 O 2 mole C 2 H gram C 2 H grams H 2 O 6mole H 2 O 1 mole C 2 H grams C 2 H 6 2) Given this balanced equation 2 Al(s) + 6 HCl(aq) 2 Al(NO3)3(aq) + 3 H2(gas) How many LITERS of hydrogen gas are produced when 567 grams HCl completely STP? 567 grams HCl 1 mole HCl 3 mole H Liters H grams HCl 6 mole HCl 1 mole H2 174 liters H 2 3) Given this balanced equation N2 (g) + 3 H2(g) 2 NH3(g) (a) How many particles of H 2 reacted when 444 grams of NH 3 were produced? 444 grams of NH 3 1 mole NH 3 3 mole H x particles H grams NH 3 2 mole NH 3 1 mole H x Particles H2

5 4) Given this balanced equation 2Fe + 6 HCl - 2FeCl3 + 3H2 A student placed 84.5 grams of Fe in a flask and reacted it with excess HCl. The student had a lab yield of 3.76 grams H2. THIS IS THE LAB YIELD What was the theoretical yield for this reaction? solve for grams H g Fe 1 mole Fe 3 mole H grams H grams H grams Fe 2 mole Fe 1 mole H2 What is the student s percent yield? Need lab yield from above 3.76 grams H2 Need theoretical yield from answer box 4.54 grams H2 % yield is LAB yield DIVIDED by THEORETICAL yield Times grams H 2 x % 4.54 grams H 2 yield