What weight of sodium hydroxide is required to neutralise $100 \ mL$ of $0.1 \ N - HCl$ (in $g$)?

For the combustion reaction $C_2H_{6(g)} + nO_{2(g)} \to CO_{2(g)} + H_2O_{(l)}$,what is the ratio of the stoichiometric coefficients of $CO_2$ and $H_2O$ in the balanced equation?

Complete combustion of $3 \ g$ of ethane gives $x \times 10^{22}$ molecules of water. The value of $x$ is ......... (Round off to the Nearest Integer). [Use: $N_{A} = 6.023 \times 10^{23} ;$ Atomic masses in $u$ $C = 12.0, O = 16.0, H = 1.0$]

What amount of oxygen is used at $S.T.P$ to obtain $9 \ g$ water from a sufficient amount of hydrogen gas (in $dm^3$)?

The most abundant elements by mass in the body of a healthy human adult are: Oxygen $(61.4\%);$ Carbon $(22.9\%),$ Hydrogen $(10.0\%);$ and Nitrogen $(2.6\%).$ The weight which a $75 \ kg$ person would gain if all $^1H$ atoms are replaced by $^2H$ atoms is ....... $kg$.

Calculate the amount of water $(g)$ produced by the combustion of $16 \ g$ of methane. (in $g$)