Which sample contains the largest number of atoms?

The density of an equimolar mixture of $CH_4$ and $CO$ at $STP$ is ............... $g \, L^{-1}$.

What is the actual volume occupied by water molecules present in $20 \ cm^3$ of water (in $cm^3$)?

$20 \ mL$ of $2 \ M$ $NaOH$ solution is added to $400 \ mL$ of $0.5 \ M$ $NaOH$ solution. The final concentration of the solution is $.......... \times 10^{-2} \ M$. $(Nearest \ integer)$.

If the density of methanol is $0.793 \, kg \, L^{-1}$,what is its volume needed for making $2.5 \, L$ of its $0.25 \, M$ solution (in $, mL$)?

When $400 \ mL$ of $0.2 \ M \ H_2SO_4$ is mixed with $600 \ mL$ of $0.1 \ M \ NaOH$, the heat evolved is $3.43 \ kJ$. If the specific heat of water is $4.18 \ J \ K^{-1} \ g^{-1}$, the rise in temperature of the final solution will be ........... $K$. (Assume the specific heat capacity of the final solution is the same as that of water)