How many grams of a dibasic acid (molar mass $= 200$) are present in $100 \, mL$ of its aqueous solution to make its strength $0.1 \, N$ (decinormal)?

When $500 \ mL$ of a gaseous hydrocarbon is burned in excess of $O_2$,it produces $2.5 \ L$ of $CO_2$ and $3.0 \ L$ of water vapor. What is the molecular formula of the hydrocarbon?

What is the percentage atom economy during the conversion of reactant to product if the formula weight of reactants is $246 \ u$ and that of the product is $123 \ u$ (in $\%$)?

For the given series of reactions:
$NH_{3(g)} + O_{2(g)} \rightarrow NO_{(g)} + H_2O_{(l)}$
$NO_{(g)} + O_{2(g)} \rightarrow NO_{2(g)}$
To obtain the maximum mass of $NO_2$ from a given mass of a mixture of $NH_3$ and $O_2$,the ratio of the mass of $NH_3$ to $O_2$ should be:

At $298 \ K$,equal volumes of $SO_2, CH_4$ and $O_2$ are mixed in an empty container. The total pressure exerted is $2.1 \ atm$. The partial pressure of $CH_4$ in the mixture is $.......... \ atm$.

What is the value of $w$ (mass of solute in grams) required to prepare a definite volume of a standard solution of known normality $(N)$?
[$N = \text{normality}$,$E = \text{equivalent weight}$,$V = \text{volume of solution in } mL$]