# Quiz - Balancing Equations | Fundamentals of Chemical Reactions

1

The reaction of ethanol, C2H5OH, with oxygen is a popular classroom demonstration. Balance the equation to find the number of moles of gaseous products formed per mole of ethanol. _ C2H5OH (g) + _O2  (g) → _ CO(g) + _ H2O (g)

The balanced equation is: C2H5OH + 3 O→ 2 CO+ 3 H2O This shows that 2 moles of CO2 and 3 moles of H2O are produced per mole of ethanol, summing up to 5 moles of gaseous products.

2

Acetylene, C2H2, reacts with oxygen according to the unbalanced equation: C2H2 (g) + O2 (g) → CO2 (g) + H2O (g). What is the O2/C2H2 ratio when this equation is correctly balanced?

The balanced equation is: 2 C2H2 (g) + 5 O2 (g) → 4 CO2 (g) + 2 H2O (g). This shows that 5 moles of O2 are required for 2 moles of C2H2, resulting in an O2/C2H2 ratio of 5/2.

3

Balance the following chemical equation: C7​H1​6 + O​→ CO2​ + H2​O. What is the coefficient of O2​ after balancing?

The balanced equation is C7​H1​6 + 11 O​→ 7 CO2​ + 8 H2​O, so the coefficient of O2​ is 11.

4

Balance the following chemical equation: Fe2​O​+ C → Fe + CO2​. What is the coefficient of Fe after balancing?

The balanced equation is 2 Fe2​O​+ 3 C → 4 Fe + 3 CO2, so the coefficient of Fe is 4.

5

Balance the following chemical equation: H3​PO4​ + Ca(OH)2​ → Ca3​(PO4​)2​ + H2​O. What is the coefficient of H2O after balancing?

The balanced equation is 2 H3​PO4​ + 3 Ca(OH)2​ → Ca3​(PO4​)2​ + 6 H2​O, so the coefficient of H2O is 6.

6

Balance the following chemical equation: K2​Cr2​O7​ + H2​SO4​ + FeSO4​ → K2​SO4​ + Fe2​(SO4​)3​ + Cr2​(SO4​)3​ + H2​O. What is the coefficient of FeSO4​ after balancing?

The balanced equation is K2​Cr2​O7​ + 7 H2​SO4​ + 6 FeSO4​ → K2​SO4​ + 3 Fe2​(SO4​)3​ + Cr2​(SO4​)3​ + 7 H2​O, so the coefficient of FeSO4​ is 6.

7

What is the coefficient for O2 when the following reaction As2S3 + O2 → As2O3 + SO2 is correctly balanced with the smallest integer coefficients?

The balanced chemical equation is: 2 As2S3 + 9 O2 → 2 As2O3 + 6 SO2 This shows that the coefficient for O2 is 9.

8

When this equation is balanced using the smallest possible integers, what is the sum of the coefficients?
(NH4)3PO4 (aq) + CaCl2 (aq) → Ca3(PO4)2 (s) + NH4Cl (aq)

The balanced equation is: 2 (NH4)3PO4 (aq) + 3 CaCl2 (aq) → Ca3(PO4)2 (s) + 6 NH4Cl (aq). The sum of the coefficients is 2 + 3 + 1 + 6 = 12.