Chapter 7 Pearson Questions - Gen Chem 1 Lecture

Balance the following equation.

B₂H₆(g) + O₂(g) → B₂O₃(s) + H₂O(g)

What is the stoichiometric coefficient for oxygen?

2

3

6

4

1

Answer: 3

Explanation:

B2H6(g) + O2(g) → B2O3(s) + H2O(g)
6 H | 2H
2 B | 2B
2 O | 4O

B2H6(g) + O2(g) → B2O3(s) + (3) H2O(g)
6 H | 6H
2 B | 2B
2 O | 6O

B2H6(g) + (3) O2(g) → B2O3(s) + (3) H2O(g)
6 H | 6H
2 B | 2B
6 O | 6O

According to the following balanced reaction, how many moles of NO are formed from 8.44 moles of NO₂ if there is plenty of water present?

3 NO₂(g) + H₂O(l) → 2 HNO₃(aq) + NO(g)

2.82 moles NO

25.32 moles NO

12.66 moles NO

8.44 moles NO

5.63 moles NO

Answer: 2.82 moles NO

Explanation:

fraction comes from the balanced equation

                                  1 moles NO 

8.44 moles NO₂  *   _______________  =  2.82 moles NO

                                    3 moles NO₂ 

Consider the following reaction. How many moles of oxygen are required to produce 8.00 moles of water? Assume that there is excess C₃H₇SH present.

C₃H₇SH(l) + 6 O₂(g) → 3 CO₂(g) + SO₂(g) + 4 H₂O(g)

2.00 moles O₂

8.00 moles O₂

12.0 moles O₂

5.33 moles O₂

32.0 moles O₂

Answer: 12.0 moles O₂

Explanation:

6 moles of oxygen are needed to produce 4 moles of water

That makes the ratio:

6 moles O₂
——————- * 8 moles H₂O = 12 moles O₂
4 moles H₂O

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