Question

1. which of the following has the highest mass?

50.0 l of oxygen at stp
50.0 g water
50.0 molecules carbon dioxide
50.0 mol nacl

Explanation:

Step1: Calculate mass of \(O_2\) at STP

At STP, 1 mol of gas = 22.4 L. Molar mass of \(O_2 = 32\space g/mol\). Moles of \(O_2=\frac{50.0\space L}{22.4\space L/mol}\approx2.232\space mol\). Mass \(= 2.232\space mol\times32\space g/mol\approx71.42\space g\).

Step2: Mass of water is given as 50.0 g.

Step3: Calculate mass of \(CO_2\)

Molar mass of \(CO_2 = 44\space g/mol\). Moles of \(CO_2=\frac{50.0\space molecules}{6.022\times10^{23}\space molecules/mol}\approx8.303\times10^{-23}\space mol\). Mass \(= 8.303\times10^{-23}\space mol\times44\space g/mol\approx3.653\times10^{-21}\space g\).

Step4: Calculate mass of \(NaCl\)

Molar mass of \(NaCl = 58.44\space g/mol\). Mass \(= 50.0\space mol\times58.44\space g/mol = 2922\space g\).

Answer:

50.0 mol NaCl