$K_2CS_3$ can be called potassium:

$1 \ g$ equivalent of a substance is present in:

$25 \ mL$ of $0.1 \ N \ NaOH$ solution neutralises $12.5 \ mL$ of $HCl$ solution. The amount of water needed to convert $500 \ mL$ of such $HCl$ solution to $0.1 \ N$ is (in $mL$)

$A + 2B \rightarrow AB_{2}$. $36.0 \ g$ of '$A$' (Molar mass: $60 \ g \ mol^{-1}$) and $56.0 \ g$ of '$B$' (Molar mass: $80 \ g \ mol^{-1}$) are allowed to react. Which of the following statements are correct?
$(A)$ '$A$' is the limiting reagent
$(B)$ $77.0 \ g$ of $AB_{2}$ is formed
$(C)$ Molar mass of $AB_{2}$ is $220 \ g \ mol^{-1}$
$(D)$ $15.0 \ g$ of '$A$' is left unreacted after the completion of reaction.
Choose the correct answer from the options given below:

Suppose you have to determine the percentage of carbon dioxide in a sample of a gas available in a container. Which is the best absorbing material for the carbon dioxide?

Mole fraction of $O_2$ in $O_2$ and $O_3$ mixture is $0.25$. Hence percentage concentration $\left( \frac{w}{W} \% \right)$ of $O_2$ in the mixture is: