The molarity of $0.2 \ N$ $Na_2CO_3$ solution will be (in $M$)

How many grams of ethanol are required to obtain $280 \ mL$ of dihydrogen gas at $S.T.P.$ by the reaction of $C_2H_5OH$ with $Na$ metal? (Molar mass of ethanol = $46 \ g/mol$)

$5 \ g$ of $NaOH$ was dissolved in deionized water to prepare a $450 \ mL$ stock solution. What volume (in $mL$) of this solution would be required to prepare $500 \ mL$ of $0.1 \ M$ solution?
Given: Molar Mass of $Na$,$O$,and $H$ is $23$,$16$,and $1 \ g \ mol^{-1}$ respectively.

$A$ flask is weighed when filled with methane $(CH_4)$. The methane is then removed,and the flask is weighed again. When the flask is filled with oxygen $(O_2)$ at the same temperature and pressure,the mass of oxygen will be:

Calculate the volume of $99 \text{ g}$ of $CO_2$ at $STP$. (in $\text{ L}$)

$C_2H_4$ can react with $H_2$ in the presence of a catalyst to form $C_2H_6$ as per the following reaction: $C_2H_{4(g)} + H_{2(g)} \xrightarrow{\text{Catalyst}} C_2H_{6(g)}$. The amount of $C_2H_4$ in grams required to produce $50 \ g$ of $C_2H_6$ is: (in $g$)