Nitroglycerine, ${{\text{C}}_3}{{\text{H}}_5}{{\text{N}}_3}{{\text{O}}_{\text{9}}}$, can be used in the manufacture of explosives. What is the coefficient of ${{\text{C}}_3}{{\text{H}}_5}{{\text{N}}_3}{{\text{O}}_9}({\text{l)}}$ when the equation for its decomposition reaction is balanced using the lowest whole numbers?

___ ${{\text{C}}_3}{{\text{H}}_5}{{\text{N}}_3}{{\text{O}}_9}{\text{(l)}} \to$ ___ ${\text{C}}{{\text{O}}_2}{\text{(g)}} +$ ___ ${{\text{H}}_2}{\text{O(l)}} +$ ___ ${{\text{N}}_2}{\text{(g)}} +$ ___ ${{\text{O}}_2}{\text{(g)}}$

A.     2

B.     4

C.     20

D.     33

B

One respondent stated that this question was particularly difficult. Although the question was challenging, 66.89% of candidates did manage to get the correct answer B. The question was the ninth hardest question on the paper.