Some Basic Concepts of Chemistry PYQs

The number of hydrogen atoms present in 5.4 g of urea is: (Given: Molar mass of urea = 60 g mol⁻¹; Nₐ = 6.022 × 10²³ particles mol⁻¹)

Dalton’s Atomic theory could not explain which of the following?

Among the following, choose the ones with equal number of atoms. A. 212 g of Na₂CO₃(s) [molar mass = 106 g] B. 248 g of Na₂O(s) [molar mass = 62 g] C. 240 g of NaOH(s) [molar mass = 40 g] D. 12 g of H₂(g) [molar mass = 2 g] E. 220 g of CO₂(g) [molar mass = 44 g] Choose the correct answer from the options given below :

The highest number of helium atoms is in:

1 gram of sodium hydroxide was treated with 25 mL of 0.75 M HCl solution, the mass of sodium hydroxide left unreacted is equal to:

A compound X contains 32% of A, 20% of B and remaining percentage of C. The empirical formula of X is: (Given atomic masses of A = 64 u, B = 40 u, C = 32 u)

Select the correct statements from the following: A. Atoms of all elements are composed of two fundamental particles. B. The mass of the electron is 9.10939 × 10⁻³¹ kg. C. All the isotopes of a given element show same chemical properties. D. Protons and electrons are collectively known as nucleons. E. Dalton’s atomic theory regarded the atom as an ultimate particle of matter. Choose the correct answer from the options given below:

The right option for the mass of CO₂ produced by heating 20 g of 20% pure limestone is: (Atomic mass of Ca = 40)

What mass of 95% pure CaCO₃ will be required to neutralise 50 mL of 0.5 M HCl solution according to the reaction: CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + CO₂(g) + 2H₂O(l) [Calculate up to second place of decimal point]

An organic compound contains 78% (by wt.) carbon and remaining percentage of hydrogen. The right option for empirical formula of this compound is: [Atomic wt. of C is 12, H is 1]

Choose the correct option for the total pressure (in atm.) in a mixture of 4 g O₂ and 2 g H₂ confined in a total volume of one litre at 0°C. [Given R = 0.082 L atm mol⁻¹ K⁻¹, T = 273 K]

Which one of the followings has maximum number of atoms?

In which case is number of molecules of water maximum?

The number of water molecules is maximum in:

If Avogadro number $N_A$ is changed from $6.022 \times 10^{23}\ \mathrm{mol^{-1}}$ to $6.022 \times 10^{20}\ \mathrm{mol^{-1}}$, this would change:

20.0 g of a magnesium carbonate sample decomposes on heating to give carbon dioxide and 8.0 g magnesium oxide. What will be the percentage purity of magnesium carbonate in the sample? (Atomic weight: Mg = 24)

What is the mass of the precipitate formed when 50 mL of 16.9% solution of AgNO₃ is mixed with 50 mL of 5.8% NaCl solution? (Ag = 107.8, N = 14, O = 16, Na = 23, Cl = 35.5)

When 22.4 litres of H₂(g) is mixed with 11.2 litres of Cl₂(g) each at S.T.P., the moles of HCl(g) formed is equal to:

1.0 g of magnesium is burnt with 0.56 g O₂ in a closed vessel. Which reactant is left in excess and how much? (At. wt. Mg = 24 ; O = 16)

Which has the maximum number of molecules among the following?

The pressure exerted by 6.0 g of methane gas in a 0.03 m³ vessel at 129°C is (Atomic masses: C = 12.01, H = 1.01, R = 8.314 J K⁻¹ mol⁻¹):

10 g of hydrogen and 64 g of oxygen were filled in a steel vessel and exploded. Amount of water produced in this reaction will be:

What is the $[OH^-]$ in the final solution prepared by mixing $20.0\,mL$ of $0.050\,M$ HCl with $30.0\,mL$ of $0.10\,M$ $Ba(OH)_2$?

How many moles of lead(II) chloride will be formed from a reaction between 6.5 g of PbO and 3.2 g of HCl?

Volume occupied by one molecule of water (density = 1 g cm⁻³) is

An organic compound contains carbon, hydrogen and oxygen. Its elemental analysis gave C = 38.71% and H = 9.67%. The empirical formula of the compound would be