The number of moles of $SO_2Cl_2$ in $13.5 \ g$ is

The number of atoms in $8 \ g$ of sodium is $x \times 10^{23}$. The value of $x$ is ...... (Nearest integer).
$[ \text{Given}: N_{A} = 6.02 \times 10^{23} \ mol^{-1}, \text{Atomic mass of } Na = 23.0 \ u ]$

Find the number of molecules,number of carbon atoms,number of hydrogen atoms,and total number of atoms in $5.6 \ L$ of $CH_4$ at $STP$.

The number of $N$ atoms in $681 \ g$ of $C_{7}H_{5}N_{3}O_{6}$ is $x \times 10^{21}$. The value of $x$ is $.....$ $(N_{A} = 6.02 \times 10^{23} \ mol^{-1})$ (Nearest Integer)

$A$ gas mixture contains $50\%$ helium and $50\%$ methane by volume. What is the percent by weight of methane in the mixture?

There are $6.02 \times 10^{22}$ molecules each of $N_2$,$O_2$,and $H_2$ which are mixed together at $760 \ mm$ and $273 \ K$. The mass of the mixture in grams is: