What is the percentage atom economy when the formula weight of the desired product is $65 \text{ u}$ and the sum of the formula weights of all reactants is $130 \text{ u}$ (in $\%$)?

How many $g$ of a dibasic acid (Mol. wt. $= 200$) should be present in $100 \ mL$ of its aqueous solution to give decinormal strength?

$100 \, mL$ of $0.1 \, N \, HCl$ is neutralized by $0.2 \, N \, NaOH$ solution. After adding $30 \, mL$ of $NaOH$ solution,the neutralization is continued using $0.25 \, N \, KOH$. Calculate the volume of $KOH$ in $mL$ required to complete the neutralization.

How many moles of methane are required in the combustion reaction of methane to produce $22 \ g$ of $CO_{2(g)}$ (in $mol$)?

$A$ solution of $CaCl_2$ is $0.5 \, mol/L$. The number of moles of chloride ions in $500 \, mL$ of this solution will be:

Hardness of water is $200 \ ppm$. Calculate the molarity and normality of $CaCO_3$ in the water.