Question

practice problems
sample problem 1: determine the number of moles of oxygen that are needed to react with 0.56mol of vanadium to form divanadium pentoxide, v₂o₅. (ans.0.70mol o₂)
4v + 5o₂ → 2v₂o₅
\frac{unknown}{known}
\frac{n(o)}{0.56} = \frac{5}{4}
n= 0.7mol

1. nitrogen can combine with oxygen to form several different oxides of nitrogen. these oxides include no₂, no, n₂o.

Explanation:

Step1: Identify mole ratio from equation

The balanced equation is \(4V + 5O_2
ightarrow 2V_2O_5\). The mole ratio of \(V\) to \(O_2\) is \(4:5\). Let moles of \(V\) be \(n(V) = 0.56\space mol\) (given), moles of \(O_2\) be \(n(O_2)\) (unknown).

Step2: Set up proportion using mole ratio

From the ratio \( \frac{n(V)}{n(O_2)}=\frac{4}{5} \), substitute \(n(V) = 0.56\space mol\):
\( \frac{0.56}{n(O_2)}=\frac{4}{5} \)

Step3: Solve for \(n(O_2)\)

Cross - multiply: \(4\times n(O_2)=0.56\times5\)
\(4n(O_2) = 2.8\)
Divide both sides by 4: \(n(O_2)=\frac{2.8}{4}=0.7\space mol\)

Answer:

The number of moles of oxygen needed is \(0.7\space mol\).