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 $\%$)?

If the percentage purity of an impure sample of a compound is given,then the weight of the substance required to prepare its $0.1 \, N$ solution will be:

How many moles of $NaOH$ are present in $27 \, mL$ of $0.15 \, M \, NaOH$?

$20 \ mL$ 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 $........ M$. $(Nearest \ Integer \ value)$
$(Given: Na=23, I=127, Ag=108, N=14, O=16 \ g \ mol^{-1})$

In an experiment on the enthalpy of neutralisation of sodium hydroxide with sulphuric acid,$50 \ cm^3$ of $0.4 \ M$ sodium hydroxide were titrated thermometrically with $0.25 \ M$ sulphuric acid. Which of the following plots gives the most probable correct representation of the temperature of the solution (initial temperatures of $NaOH$ and $H_2SO_4$ are the same)?

What volume of decimolar solution should be mixed in a solution of the same solute $(0.5 \, M, \, 200 \, mL)$ to make it $0.25 \, M$?