A student performs an experiment to determine the molar mass of an unknown solid metal, \(\text{M}\). A \(0.0450\text{ g}\) sample of \(\text{M}\text{(s)}\) reacts completely with excess hydrochloric acid according to the reaction below:

\[\text{M}\text{(s)} + 2\,\text{H}^+\text{(aq)} \rightarrow \text{M}^{2+}\text{(aq)} + \text{H}_2\text{(g)}\]

The \(\text{H}_2\text{(g)}\) produced is collected over water in a gas-measuring tube at \(35^\circ\text{C}\) and a barometric pressure of \(755\text{ torr}\). The water levels inside and outside the tube are equalized before the gas volume is recorded. In calculating the molar mass of \(\text{M}\), the student uses the barometric pressure (\(755\text{ torr}\)) as the pressure of \(\text{H}_2\text{(g)}\), failing to account for the vapor pressure of water at \(35^\circ\text{C}\) (\(42.2\text{ torr}\)). Which of the following best explains how this omission affects the calculated molar mass of \(\text{M}\)?