Embibe Experts Solutions for Chapter: Some Basic Concepts of Chemistry, Exercise 4: Exercise-4

Mass of a typical star is $1.0\times {10}^{30}\mathrm{kg}$. Assume that a star is typically $3/4$ hydrogen and $1/4$  helium by mass. The estimated number of protons (which are present in $\mathrm{H}$ as well as $\mathrm{He}$) in a typical star is approximately. 

$10 \mathrm{L}$ of ${\mathrm{O}}_2 \mathrm{gas}$ is reacted with $30 \mathrm{L}$ of $\mathrm{CO} \left(\mathrm{g}\right)$ at $\mathrm{STP}.$ The volume of each gas present at the end of the reaction are:

$1$ mole of a gaseous aliphatic compound ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{3\mathrm{n}}{\mathrm{O}}_{\mathrm{m}}$ is completely burnt in an excess of oxygen. The contraction in volume is: (assume water get condensed out)

One mole of a gas is defined as:

The molar concentration of pure water at $4°\mathrm{C}$ and $1$ atm pressure is

Elevation in $\mathrm{B}.\mathrm{P}.$ of an aqueous urea solution is $0.52°\mathrm{C}. ({\mathrm{K}}_{\mathrm{b}} = 0.52° \mathrm{K} {\mathrm{mol}}^{–1} \mathrm{kg})$ Hence, mole-fraction of urea in this solution is:

The rate of the reaction ${\mathrm{MnO}}_4^{-}(\mathrm{aq}.)+8{\mathrm{H}}^{+}(\mathrm{aq}.)+5{\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right)⟶{\mathrm{Mn}}^{2+}\left(\mathrm{aq}\right)+5{\mathrm{Fe}}^{3+}(\mathrm{aq}.)+4{\mathrm{H}}_2\mathrm{O}$ can be best measured by monitoring colorimetrically. The concentration of :