Chemical equations, stoichiometry and limiting reagent — practice questions

Question 1 · difficulty L2 · understanding

The mass of iron converted into Fe 3 O 4 by the action of 18 g of steam is: (Given: Molar mass of H, O and Fe are 1, 16 and 56 g mol −1 respectively) Assume iron is present in excess:

• A. 2.1 g
• B. 4.2 g
• C. 21 g
• D. 42 g

Question 2 · difficulty L2 · understanding

Identify the correct statements : A. Hydrated salts can be used as primary standard. B. Primary standard should not undergo any reaction with air. C. Reactions of primary standard with another substance should be instantaneous and stoichiometric. D. Primary standard should not be soluble in water. E. Primary standard should have low relative molar mass. Choose the correct answer from the options given below :

• A. D and E Only
• B. A, B and E Only
• C. A, B, C and E Only
• D. A, B and C Only

Question 3 · difficulty L2 · understanding

$\mathrm{A}+2 \mathrm{~B} \longrightarrow \mathrm{AB}_2$ 36.0 g of 'A' (Molar mass : $60 \mathrm{~g} \mathrm{~mol}^{-1}$ ) and 56.0 g of ' B ' (Molar mass : $80 \mathrm{~g} \mathrm{~mol}^{-1}$ ) are allowed to react. Which of the following statements are correct ? A. 'A' is the limiting reagent. B. $77.0 \mathrm{~g}$ of $\mathrm{AB}_2$ is formed. C. Molar mass of $\mathrm{AB}_2$ is $140 \mathrm{~g} \mathrm{~mol}^{-1}$. D. $15.0 \mathrm{~g}$ of A is left unreacted after the completion of reaction. Choose the correct answer from the options given below :

• A. A and C Only
• B. A and B Only
• C. C and D Only
• D. B and D Only

Question 4 · difficulty L2 · understanding

In the reaction, $$2 \mathrm{Al}(\mathrm{~s})+6 \mathrm{HCl}(\mathrm{aq}) \rightarrow 2 \mathrm{Al}^{3+}(\mathrm{aq})+6 \mathrm{Cl}^{-}(\mathrm{aq})+3 \mathrm{H}_2(\mathrm{~g})$$

• A. $12 \mathrm{~L} \,\mathrm{HCl}(\mathrm{aq})$ is consumed for every $6 \mathrm{~L} \,\mathrm{H}_2(\mathrm{~g})$ produced.
• B. $11.2 \mathrm{~L} \,\mathrm{H}_2(\mathrm{~g})$ at STP is produced for every mole of HCl consumed.
• C. $33.6 \mathrm{~L} \,\mathrm{H}_2(\mathrm{~g})$ is produced regardless of temperature and pressure for every mole of Al that reacts.
• D. $67.2 \mathrm{~L} \,\mathrm{H}_2(\mathrm{~g})$ at STP is produced for every mole of Al that reacts.

Question 5 · difficulty L2 · understanding

Aqueous HCl reacts with MnO 2 (s) to form MnCl 2 (aq), Cl 2 (g), and H 2 O(l). What is the weight (in g) of Cl 2 liberated when 8.7 g of MnO 2 (s) is reacted with excess aqueous HCl solution? (Given Molar mass in g mol −1 Mn = 55, Cl = 35.5, O = 16, H = 1)

• A. 14.2
• B. 21.3
• C. 7.1
• D. 71

Question 6 · difficulty L2 · understanding

14.0 g of calcium metal is allowed to react with excess HCl at 1.0 atm pressure and 273 K . Which of the following statements is incorrect? [Given : Molar mass in $\mathrm{g} \mathrm{mol}^{-1}$ of $\mathrm{Ca}-40, \mathrm{Cl}-35.5, \mathrm{H}-1$ ]

• A. The limiting reagent is calcium metal.
• B. 33.3 g of $\mathrm{CaCl}_2$ is produced.
• C. 7.84 L of $\mathrm{H}_2$ gas is evolved.
• D. 0.35 mol of $\mathrm{H}_2$ gas is evolved.

Question 7 · difficulty L2 · understanding

Mass of magnesium required to produce 220 mL of hydrogen gas at STP on reaction with excess of dil. HCl is Given: Molar mass of Mg is $24 \mathrm{~g} \mathrm{~mol}^{-1}$.

• A. 0.24 mg
• B. 235.7 g
• C. 2.444 g
• D. 236 mg

Question 8 · difficulty L2 · understanding

Combustion of glucose $$(\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6)$$ produces $$\mathrm{CO}_2$$ and water. The amount of oxygen (in $$\mathrm{g}$$) required for the complete combustion of $$900 \mathrm{~g}$$ of glucose is : [Molar mass of glucose in $$\mathrm{g} \mathrm{~mol}^{-1}=180$$]

• A. 32
• B. 480
• C. 800
• D. 960

Question 9 · difficulty L2 · understanding

When a hydrocarbon A undergoes complete combustion it requires 11 equivalents of oxygen and produces 4 equivalents of water. What is the molecular formula of $A$ ?

• A. $\mathrm{C}_{9} \mathrm{H}_{8}$
• B. $\mathrm{C}_{5} \mathrm{H}_{8}$
• C. $\mathrm{C}_{11} \mathrm{H}_{4}$
• D. $\mathrm{C}_{11} \mathrm{H}_{8}$

Question 10 · difficulty L2 · understanding

$$\mathrm{N}_{2(\mathrm{~g})}+3 \mathrm{H}_{2(\mathrm{~g})} \rightleftharpoons 2 \mathrm{NH}_{3(\mathrm{~g})}$$ $$20 \mathrm{~g} \quad ~~~5 \mathrm{~g}$$ Consider the above reaction, the limiting reagent of the reaction and number of moles of $$\mathrm{NH}_{3}$$ formed respectively are :

• A. $$\mathrm{H}_{2}, 1.42$$ moles
• B. $$\mathrm{H}_{2}, 0.71$$ moles
• C. $$\mathrm{N}_{2}, 1.42$$ moles
• D. $$\mathrm{N}_{2}, 0.71$$ moles