Embibe Experts Solutions for Chapter: Some Basic Concepts of Chemistry, Exercise 1: KEAM 2019

Experimentally it was found that a metal oxide has formula ${\mathrm{M}}_{0.98}\mathrm{O}.$ Metal $\mathrm{M}$ is present as ${\mathrm{M}}^{2+}$ adn ${\mathrm{M}}^{3+}$ in its oxide. Fraction of the metal which exists as ${\mathrm{M}}^{3+}$ would be :

Which one of the following will have the largest number of atoms?

On passing silent electric discharge through oxygen in an ozoniser, $5.5 \mathrm{mol}\%$ of oxygen is converted to ozone. How many moles of ${\mathrm{O}}_2$ and ${\mathrm{O}}_3$ result when $35$ moles of ${\mathrm{O}}_2$ is originally present ?

An organic compound contains $24\%$ carbon, $4\%$ hydrogen and remaining chlorine. Its empirical formula is

The standard enthalpies of formation of ${\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$ and ${\mathrm{CO}}_2\left(\mathrm{g}\right)$ are respectively $-286\mathrm{kJ} {\mathrm{mol}}^{-1}$ and $-394\mathrm{kJ} {\mathrm{mol}}^{-1}$. If the standard heat of combustion of ${\mathrm{CH}}_4\left(\mathrm{g}\right)$ is $-891\mathrm{kJ} {\mathrm{mol}}^{-1},$ then the standard enthalpy of formation of ${\mathrm{CH}}_4\left(\mathrm{g}\right)$ is

A solution is prepared by dissolving $20\mathrm{g} \mathrm{NaOH}$ in $1250\mathrm{mL}$ of a solvent of density $0.8\mathrm{g}/\mathrm{mL}.$ Then the molality of the solution is;

At $100°\mathrm{C}$ and $1 \mathrm{atm},$ if the density of the liquid water is $1.0 {\mathrm{gcm}}^{-3}$ and that of water vapour is $0.0006{\mathrm{gcm}}^{-3},$ then the volume occupied by water molecules in $1 \mathrm{L}$ of steam at this temperature is

A solution of methanol in water is $20\%$ by volume. If the solution and pure methanol have densities of $0.964 \mathrm{kg}{\mathrm{L}}^{-1}$ and $0.793 \mathrm{kg}{\mathrm{L}}^{-1},$
respectively, find the percent of methanol by weight ?