Question

1. 500 mL C2H6 was measured at STP, Determine how many grams of C2H6 were measured.

2. The mass percentage composition of sodium metal in 58.44 g NaCl is about 39.34%, Determine the percentage composition of sodium in 1000 g of NaCl.

Answer 1

Question 1

$\nu=\frac{m}{M}=\frac{V}{V_m}$ whence $m=\frac{VM}{V_m}$

$M(C_2H_6)=110\frac{gram}{mole}$

Molar volume $V_m=22.4$ (L)

$m=\frac{500*10^{-3}*110}{22.4}=2.5$ (g)

Question 2:

If W is the mass percentage, it has the linear dependence from mass.

$W_1-m_1 W_2-m_2$

$\frac{W_1}{W_2}=\frac{m_1}{m_2}$

$W_2=\frac{m_2}{m_1}W_1$

$W_2=\frac{1000}{58.44}*0.3934=0.023=6.73$ (it's a very big number)