NCERT Solutions for Chapter: Some Basic Concepts of Chemistry, Exercise 1: Long Answer Type

A vessel contains $1.6 \mathrm{g}$ of dioxygen at STP ($273.15\mathrm{K}, 1$$\mathrm{atm}$ pressure). The gas is now transferred to another vessel at a constant temperature, where pressure becomes half of the original pressure. Calculate the volume of the new vessel.

A vessel contains $1.6 \mathrm{g}$ of dioxygen at STP ($273.15\mathrm{K}, 1$atm pressure). The gas is now transferred to another vessel at a constant temperature, where pressure becomes half of the original pressure. Calculate the number of molecules of dioxygen. 

Calcium carbonate reacts with aqueous $\mathrm{HCl}$ to give ${\mathrm{CaCl}}_2$ and ${\mathrm{CO}}_2$ according to the reaction given below:

${\mathrm{CaCO}}_3\left(\mathrm{s}\right)+2\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{CaCl}}_2\left(\mathrm{aq}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

What mass of ${\mathrm{CaCl}}_2$ will be formed when $250 \mathrm{mL}$ of $0.76 \mathrm{M} \mathrm{HCl}$ reacts with $1000 \mathrm{g}$ of ${\mathrm{CaCO}}_3$? Name the limiting reagent. Calculate the number of moles of ${\mathrm{CaCl}}_2$ formed in the reaction. 

Define the law of multiple proportions. Explain it with two examples. How does this law point to the existence of atoms?

A box contains some identical red coloured balls, labelled as $\mathrm{A}$, each weighing $2$ grams. Another box contains identical blue coloured balls, labelled as $\mathrm{B}$, each weighing $5$ grams. Consider the combinations $\mathrm{AB}, {\mathrm{AB}}_2, {\mathrm{A}}_2\mathrm{B} \mathrm{and} {\mathrm{A}}_2{\mathrm{B}}_3$ and show that the law of multiple proportions is applicable.