Calculate percentage atom economy when $46 \ g$ ethanol is obtained from $64.5 \ g$ chloroethane and $56 \ g$ $KOH_{(aq)}$. (in $\%$)

An iron alloy contains $54.7\%$ iron and has a density of $8.17 \, g \, cm^{-3}$. What is the number of iron atoms in an alloy block of dimensions $10 \, cm \times 15 \, cm \times 20 \, cm$?

$20 \ mL$ of sodium iodide solution gave $4.74 \ g$ silver iodide when treated with excess of silver nitrate solution. The molarity of the sodium iodide solution is $........ M$. $(Nearest \ Integer \ value)$
$(Given: Na=23, I=127, Ag=108, N=14, O=16 \ g \ mol^{-1})$

The number of moles of hydrogen molecules required to produce $20$ moles of ammonia through Haber's process is

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A:$ $3.1500 \ g$ of hydrated oxalic acid dissolved in water to make $250.0 \ mL$ solution will result in $0.1 \ M$ oxalic acid solution.
Reason $R:$ Molar mass of hydrated oxalic acid is $126 \ g \ mol^{-1}$.
In the light of the above statements,choose the correct answer from the options given below:

$0.63 \ g$ of oxalic acid is dissolved to obtain $250 \ cm^3$ of its solution. Find the normality of this solution. [Oxalic acid: $(COOH)_2 \cdot 2H_2O$] (in $N$)