Haemoglobin contains $0.33\%$ of iron by weight. The molecular weight of haemoglobin is approximately $67200$. The number of iron atoms (At. wt. of $Fe = 56$) present in one molecule of haemoglobin is

What will be the volume of $O_2$ gas at $STP$ for complete combustion of $7.8 \ g$ acetylene? ............ $L$

$5 \ mL$ of $N \ HCl$,$20 \ mL$ of $N/2 \ H_2SO_4$,and $30 \ mL$ of $N/3 \ HNO_3$ are mixed together and the volume is made up to $1 \ L$. The normality of the resulting solution is:

Three moles of $B_2H_6$ are completely reacted with methanol. The number of moles of boron containing product formed is

Fortification of food with iron is done using $FeSO_4 \cdot 7 H_2 O$. The mass in grams of the $FeSO_4 \cdot 7 H_2 O$ required to achieve $12 \ ppm$ of iron in $150 \ kg$ of wheat is $..........$ (Nearest integer).
[Given: Molar mass of $Fe, S$ and $O$ respectively are $56, 32$ and $16 \ g \ mol^{-1}$]

How many grams of $NaCl$ are decomposed by $4.9 \ g$ of $H_2SO_4$ to produce sodium hydrogen sulfate and $1.825 \ g$ of $HCl$? $[Na = 23, Cl = 35.5, S = 32, H = 1, O = 16]$