Calculate the percent atom economy when a product of formula weight $175 \ u$ is obtained in a chemical reaction using $225 \ u$ formula weight reactant. (in $\%$)

$5.85 \, g$ of $NaCl$ is dissolved in $1 \, L$ of pure water. Calculate the total number of ions in $1 \, mL$ of this solution.

Galena (an ore) is partially oxidized by passing air through it at high temperature. After some time,the passage of air is stopped,but the heating is continued in a closed furnace such that the contents undergo self-reduction. The weight (in $kg$) of $Pb$ produced per $kg$ of $O_2$ consumed is $. . . . .$ (Atomic weights in $g \ mol^{-1}: O = 16, S = 32, Pb = 207$)

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)?

In the complete combustion of $C_4H_{10}$,the number of moles of oxygen required is:

When $100 \, ml$ of $0.1 \, M$ $H_2SO_4$ reacts with $Na_2CO_3$, how many liters of $CO_2$ will be produced at $STP$ (in $L$)?