What quantity of $H_2O$ in grams is present in $0.25 \text{ mol}$ of it (in $\text{ g}$)?

$A$ thin layer of cobalt is deposited on a plate with a total area of $0.5 \ m^2$ and a thickness of $0.005 \ cm$. How many cobalt atoms are deposited on the plate? (Density of cobalt $= 8.9 \ g \ cm^{-3}$,Atomic mass of $Co = 59 \ g \ mol^{-1}$)

The number of molecules of $CO_2$ present in $44 \ g$ of $CO_2$ is

The mass of $4.48 \ dm^3$ of a certain gas is $5.6 \ g$ at $STP$. Assuming ideal behaviour,identify the probable gas from the following.

What is the concentration of water?

Which of the following statements is incorrect?