Which of the following species has the highest mass?

The more commonly used baking powder contains about $30\%$ $NaHCO_3$,$20\%$ $NaAl(SO_4)_2$,$10\%$ $Ca(H_2PO_4)_2$ and $40\%$ starch. Which of the following statements is/are correct?

Blue vitriol is

$100 \ g$ of a mixture of $NaOH$ and $Na_2SO_4$ is neutralized by $100 \ mL$ of $0.5 \ M \ H_2SO_4$. What is the amount of $Na_2SO_4$ present in the mixture (in $g$)?

Dinitrogen and dioxygen react with each other to form different compounds. The experimental data is given below:

Mass of Dinitrogen	Mass of Dioxygen
$(i) \ 14 \ g$	$16 \ g$
$(ii) \ 14 \ g$	$32 \ g$
$(iii) \ 28 \ g$	$32 \ g$
$(iv) \ 28 \ g$	$80 \ g$

$(a)$ Which law of chemical combination is followed by the above experimental data? State the law.
$(b)$ Fill in the blanks in the following conversions:
$(i) \ 1 \ km = \dots \ mm = \dots \ pm$
$(ii) \ 1 \ mg = \dots \ kg = \dots \ ng$
$(iii) \ 1 \ mL = \dots \ L = \dots \ dm^3$

$50 \ mL$ of $10 \ N \ H_2SO_4$,$25 \ mL$ of $12 \ N \ HCl$,and $40 \ mL$ of $5 \ N \ HNO_3$ were mixed together,and the volume of the mixture was made $1000 \ mL$ by adding water. The normality of the resultant solution will be.....$N$.