Laws of chemical combination — NEET & JEE Questions

Question 1 · difficulty L1 · recall

The law of conservation of mass states that in a chemical reaction

• A. mass is neither created nor destroyed
• B. mass always increases
• C. mass always decreases
• D. atoms disappear when products form

Question 2 · difficulty L2 · understanding

56.0 L of nitrogen gas is mixed with excess hydrogen gas and it is found that 20 L of ammonia gas is produced. The volume of unused nitrogen gas is found to be _________ L.

Question 3 · difficulty L2 · understanding

Blister copper is produced by reaction of copper oxide with copper sulphide. 2Cu 2 O + Cu 2 S $$\to$$ 6Cu + SO 2 When 2.86 $$\times$$ 10 3 g of Cu 2 O and 4.77 $$\times$$ 10 3 g of Cu 2 S are used for reaction, the mass of copper produced is _____________ g. (nearest integer) (Atomic mass of Cu = 63.5 a.m. u, S = 32.0 a.m. u, O = 16.0 a.m. u)

Question 4 · difficulty L2 · understanding

The moles of methane required to produce 81 g of water after complete combustion is _____________ $$\times$$ 10 $$-$$2 mol. [nearest integer]

Question 5 · difficulty L2 · understanding

A protein 'A' contains 0.30% of glycine (molecular weight 75). The minimum molar mass of the protein 'A' is __________ $$\times$$ 10 3 g mol $$-$$1 [nearest integer]

Question 6 · difficulty L2 · understanding

Number of grams of bromine that will completely react with 5.0 g of pent-1-ene is ___________ $$\times$$ 10 $$-$$2 g. (Atomic mass of Br = 80 g/mol) [Nearest Integer]

Question 7 · difficulty L2 · understanding

250 mL of 0.5 M NaOH was added to 500 mL of 1 M HCl. The number of unreacted HCl molecules in the solution after complete reaction is ___________ $$\times$$ 10 21 . (Nearest integer) (N A = 6.022 $$\times$$ 10 23 )

Question 8 · difficulty L2 · understanding

$$2MnO_4^ - + b{C_2}O_4^{2 - } + c{H^ + } \to xM{n^{2 + }} + yC{O_2} + z{H_2}O$$ If the above equation is balanced with integer coefficients, the value of c is ___________. (Round off to the Nearest Integer).

Question 9 · difficulty L2 · understanding

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

• A. Law of multiple proportion
• B. Law of gaseous volume
• C. Law of conservation of mass
• D. Law of constant proportion

Question 10 · difficulty L3 · understanding

To check the principle of multiple proportions, a series of pure binary compounds $\left(\mathrm{P}_{\mathrm{m}} \mathrm{Q}_{\mathrm{n}}\right)$ were analyzed and their composition is tabulated below. The correct option(s) is(are) Compound Weight % of $\mathrm{P}$ Weight % of $\mathrm{Q}$ 1 50 50 2 44.4 55.6 3 40 60

• A. If empirical formula of compound 3 is $P_{3} Q_{4}$, then the empirical formula of compound 2 is $\mathrm{P}_{3} \mathrm{Q}_{5}$.
• B. If empirical formula of compound 3 is $\mathrm{P}_{3} \mathrm{Q}_{2}$ and atomic weight of element $\mathrm{P}$ is 20 , then the atomic weight of $\mathrm{Q}$ is 45 .
• C. If empirical formula of compound 2 is $P Q$, then the empirical formula of the compound $\mathbf{1}$ is $\mathrm{P}_{5} \mathrm{Q}_{4}$.
• D. If atomic weight of $\mathrm{P}$ and $\mathrm{Q}$ are 70 and 35 , respectively, then the empirical formula of compound $\mathbf{1}$ is $\mathrm{P}_{2} \mathrm{Q}$.