Some Basic Concepts in Chemistry

Which of the following contain the same number of atoms ? (Given : Molar mass in g mol$^{-1}$ of H, He, O and S are 1, 4, 16 and 32 respectively) A. 2 g of $\mathrm{O_2}$ gas B. 4 g of $\mathrm{SO_2}$ gas C. 1400 mL of $\mathrm{O_2}$ at STP D. 0.05 L of He at STP E. 0.0625 mol of $\mathrm{H_2}$ gas. Choose the correct answer from the options given below :

The ratio of mass percentage (w/w) of C : H in a hydrocarbon is 12 : 1. It has two carbon atoms. The weight (in g) of $\mathrm{CO_2(g)}$ formed when 3.38 g of this hydrocarbon is completely burnt in oxygen is : (Given : Molar mass in g mol$^{-1}$ C : 12, H : 1, O : 16)

Number of moles and number of molecules in 1.4187 L of $\mathrm{SO_2}$ at STP respectively are

The correct order of total number of atoms present in (A) 2 moles of cyclohexane (B) 684 g of sucrose (C) 90.8 L of dihydrogen at STP is:

How many grams of residue is obtained by heating 2.76 g of silver carbonate? (Given : Molar mass of C, O and Ag are 12, 16 and 108 g $\mathrm{mol^{-1}}$ respectively)

What volume of hydrogen gas at STP would be liberated by action of 50 mL of $\mathrm{H_2SO_4}$ of 50% purity (density = 1.3 g mL$^{-1}$) on 20 g of zinc ? Given : Molar mass of H, O, S, Zn are 1, 16, 32, 65 g mol$^{-1}$ respectively.

An oxide of iron contains 69.9% iron, its empirical formula, is: (Given : Molar mass of Fe and O are 56 and 16 g mol$^{-1}$ respectively.)

Match List - I with List - II. List - I (Mass of substance): A. 1.8 mg water; B. 9.8 mg sulphuric acid; C. 1.8 mg carbon; D. 5.85 mg salt (NaCl). List - II (Number of atoms): I. $2\times10^{-4}\times N_A$; II. $1.5\times10^{-4}\times N_A$; III. $3\times10^{-4}\times N_A$; IV. $7\times10^{-4}\times N_A$. Choose the correct answer from the options given below :

Some $\mathrm{CO_2}$ gas was kept in a sealed container at a pressure of 1 atm and at 273 K. This entire amount of $\mathrm{CO_2}$ gas was later passed through an aqueous solution of $\mathrm{Ca(OH)_2}$. The excess unreacted $\mathrm{Ca(OH)_2}$ was later neutralized with 0.1 M of 40 mL HCl. If the volume of the sealed container of $\mathrm{CO_2}$ was x, then x is ______ cm$^3$ (nearest integer). [Given: The entire amount of $\mathrm{CO_2}$(g) reacted with exactly half the initial amount of $\mathrm{Ca(OH)_2}$ present in the aqueous solution.]

Density of 3 M NaCl solution is 1.25 g/mL. The molality of the solution is :