CHEM 101-Introductory Chemistry I- QUIZ 6 – CHAPTER 8

1. Phosphine, PH3, a reactive and poisonous compound, reacts with oxygen as follows:

4 PH3(g) + 8 O2(g) à P4O10(s) + 6 H2O(g)

If 15.0 g of phosphine reacts with sufficient oxygen, how many grams of P4O10 will be formed?

b. 31.3 g

2. Calculate the total number of moles of products that can be formed by the decomposition of 1.75 moles of ammonium nitrate, NH4NO3, according to the balanced chemical equation, 2 NH4NO3 à 2 N2 + O2 + 4 H2O

4.38 moles

Chemistry 101 Spring 2020

3. Automotive airbags inflate when sodium azide, NaN3, rapidly decomposes to its constituent elements according to the chemical equation, 2 NaN3 à 2 Na + 3 N2. How many moles of nitrogen are produced when 10000. milligrams of sodium azide decomposes?

c. 0.23077 moles

4. When we do the above reaction the very reactive element sodium is produced and must be eliminated. How many grams of sodium do we have produced that we have to get rid of?

a. 3.5385 grams

5. The reaction that is used to get rid of the sodium produced by the reaction in question 3 is sodium metal reacting with iron(III) oxide to produce sodium oxide and iron metal. Write and balance this reaction.

3Na(s) + Fe2O3(s) -> 3Na2O(s) + 2Fe(s)

6. How many moles of copper can be formed from 0.450 moles of copper(I) oxide reacting with an excess of carbon according to the reaction:

2 Cu2O + C à 4 Cu + CO2

c. 0.225 moles

7. If 20 grams of Fe2(SO4)3 is mixed with 20 grams of Ba(OH)2, according to the equation

Fe2(SO4)3 + 3 Ba(OH)2 --> 3 BaSO4 + 2 Fe(OH)3

the limiting reactant is

b. Ba(OH)2

8. How much barium sulfate product would be produced in the reaction described in question #7?

3*171.34 -> 3*233.4

20g -> (3*233.4)*20/(3*171.34)=27.24g

9. For the reaction “Burn methane (CH4)” if 28.6 grams of methane reacts with 57.6 grams of oxygen how much carbon dioxide could be produced?

ch4 16g/mol, O2 32g/mol, CO2 44g/mol

(44/64)/57.6=39.6g

10. What is the percentage yield of carbon dioxide in reaction described by question 9 if 32.1 grams of carbon dioxide are actually produced?

(32.7/39.6)*100=81%

11/12. In the reaction described by question 9 which reactant is the limiting reactant and how many moles of excess reactant are left at the end of the reaction?

14.2/16=0.8875 mole

13. The heat of reaction for burning propane (C3H8), the fuel in gas barbecues, is ∆Hrxn = - 2044 kJ. If a pork roast must absorb 1.6 x 103 kJ to fully cook, and if only 10% of the heat produced by the barbecue is actually absorbed by the roast, what mass of carbon dioxide is emitted into the atmosphere during the grilling of the pork roast?

Hrxn=-2044KJ

amount of propane=(1.6*103)/2044=0.783 moles

(0.783/10)*100=7.83 mole

mole of co2=7.83*3=23.49 mole CO2

mass of CO2=23.49*44=1033.6g CO2

14. For the reaction 2 H2 + O2 à 2 H2O ∆Hrxn = - 572.4 kJ which of the following IS NOT TRUE?

b. 572.4 kJ of heat are liberated for each mole of water formed

15. In photosynthesis, plants convert carbon dioxide and water into oxygen and glucose, C6H12O6. If 75.2 g of glucose are obtained when 131 g of CO2 react in the presence of excess H2O, what is the percent yield of the reaction?

mass of C6H12O6 =75.2g

molar mass of co2=12+2*16=44g/mol

molar mass of C6H12O6=100g

(100*131)/(6*44)=89.3g C6H12O6

(75.2*100)/89.3=84.2%

16/17. Sulfuric acid dissolves aluminum metal to produce aluminum sulfate and hydrogen gas. What is the minimum mass of sulfuric acid required to completely dissolve a block of aluminum with a mass of 22.5 grams and how much hydrogen would be produced?

(294*22.5)/54=122.5g

(6*22.5)/54=2.5g hydrogen