Mole & Solutions MCQ's PDF

1. How many moles are in 2 dm\(^3\) of a 0.5 mol dm\(^3\) NaCl solution? a) 0.25 moles b) 1 mole c) 1.5 moles d) 2 moles Answer: b) 1 mole Explanation: Number of moles (n) = concentration (c) × volume (V) = 0.5 mol dm\(^3\) × 2 dm\ (^3\) = 1 mole. 2. Calculate the concentration of...

1. How many moles are in 2 dm\(^3\) of a 0.5 mol dm\(^3\) NaCl solution? a) 0.25 moles b) 1 mole c) 1.5 moles d) 2 moles Answer: b) 1 mole Explanation: Number of moles (n) = concentration (c) × volume (V) = 0.5 mol dm\(^3\) × 2 dm\ (^3\) = 1 mole. 2. Calculate the concentration of a solution containing 0.4 moles in 2 dm\(^3\) of solution. a) 0.2 mol dm\(^3\) b) 0.4 mol dm\(^3\) c) 0.6 mol dm\(^3\) d) 1 mol dm\(^3\) Answer: a) 0.2 mol dm\(^3\) Explanation: Concentration (c) = number of moles (n) / volume (V) = 0.4 moles / 2 dm\(^3\) = 0.2 mol dm\(^3\). 3. If the concentration of K\(_2\)SO\(_4\) solution is 1.5 mol dm\(^3\) and the volume is 0.25 dm\ (^3\), what is the number of moles? a) 0.375 moles b) 0.5 moles c) 1.0 moles d) 1.25 moles Answer: a) 0.375 moles Explanation: Number of moles (n) = concentration (c) × volume (V) = 1.5 mol dm\(^3\) × 0.25 dm\(^3\) = 0.375 moles. #### Unit Conversions: 4. Convert 500 cm\(^3\) to dm\(^3\). a) 0.05 dm\(^3\) b) 0.5 dm\(^3\) c) 5 dm\(^3\) d) 50 dm\(^3\) Answer: b) 0.5 dm\(^3\) Explanation: Volume in dm\(^3\) = volume in cm\(^3\) × \(10^{-3}\). Therefore, 500 cm\(^3\) = 500 × \(10^{-3}\) dm\(^3\) = 0.5 dm\(^3\). 5. What is the volume of 1.5 moles of gas at room temperature and pressure (24 dm\(^3\) per mole)? a) 24 dm\(^3\) b) 30 dm\(^3\) c) 36 dm\(^3\) d) 48 dm\(^3\) Answer: c) 36 dm\(^3\) Explanation: Volume = moles × molar volume = 1.5 moles × 24 dm\(^3 / \)mole = 36 dm\(^3\). 6. Find the concentration of a solution if there are 2 moles in 4 dm\(^3\) of solution. a) 0.25 mol dm\(^3\) b) 0.5 mol dm\(^3\)  c) 1 mol dm\(^3\) d) 2 mol dm\(^3\) Answer: b) 0.5 mol dm\(^3\) Explanation: Concentration = number of moles / volume = 2 moles / 4 dm\(^3\) = 0.5 mol dm\ (^3\). 7. How many moles of HCl are in 250 cm\(^3\) of 1 mol dm\(^3\) HCl solution? a) 0.25 moles b) 0.5 moles c) 1 mole d) 2.5 moles Answer: a) 0.25 moles Explanation: Number of moles = concentration × volume in dm\(^3\). Volume in dm\(^3\) = 250 cm\(^3\) × \(10^{-3}\) = 0.25 dm\(^3\); therefore, moles = 1 × 0.25 = 0.25. 8. A solution has a concentration of 2 mol dm\(^3\). If you have 1 mole of the solute, what is the volume of the solution? a) 0.5 dm\(^3\) b) 1 dm\(^3\) c) 2 dm\(^3\) d) 4 dm\(^3\) Answer: a) 0.5 dm\(^3\) Explanation: Volume = number of moles / concentration = 1 mole / 2 mol dm\(^3\) = 0.5 dm\(^3\). 9. Calculate the volume in dm\(^3\) of a 0.1 mol dm\(^3\) solution containing 0.02 moles. a) 0.1 dm\(^3\) b) 0.2 dm\(^3\) c) 0.25 dm\(^3\) d) 0.5 dm\(^3\) Answer: b) 0.2 dm\(^3\) Explanation: Volume = number of moles / concentration = 0.02 / 0.1 = 0.2 dm\(^3\). 10. If you dilute 2 dm\(^3\) of a 3 mol dm\(^3\) solution to 6 dm\(^3\), what is the final concentration? a) 0.5 mol dm\(^3\) b) 1 mol dm\(^3\) c) 1.5 mol dm\(^3\) d) 2 mol dm\(^3\) Answer: b) 1 mol dm\(^3\) Explanation: \(C_1V_1 = C_2V_2\). Therefore, \( (3 \text{ mol dm}^-3) \times 2 \text{ dm}^3 = C_2 \times 6 \text{ dm}^3\); \[ C_2 = \frac{3 \times 2}{6} \text{ mol dm}^-3 = 1 \text{ mol dm}^-3 \]. 11. A 250 cm\(^3\) solution of NaOH has a concentration of 0.2 mol dm\(^3\). What is the number of moles? a) 0.025 moles b) 0.05 moles c) 0.1 moles d) 0.2 moles Answer: b) 0.05 moles Explanation: Number of moles = concentration × volume in dm\(^3\). Volume = 250 cm\(^3\) × \(10^{-3}\) dm\(^3\), thus moles = 0.2 × 0.25 = 0.05. 12. Find the volume in dm\(^3\) of 0.5 mol of H\(_2\)SO\(_4\) in a solution with a concentration of 2 mol dm\(^3\). a) 0.25 dm\(^3\) b) 0.5 dm\(^3\) c) 1 dm\(^3\) d) 2 dm\(^3\) Answer: a) 0.25 dm\(^3\) Explanation: Volume = number of moles / concentration = 0.5 mol / 2 mol dm\(^3\) = 0.25 dm\ (^3\). 13. How many moles of solute are in 500 cm\(^3\) of a 0.8 mol dm\(^3\) solution? a) 0.16 moles b) 0.32 moles c) 0.4 moles d) 1.6 moles Answer: b) 0.4 moles Explanation: Number of moles = concentration × volume. Volume = 0.5 dm\(^3\), thus moles = 0.8 × 0.5 = 0.4. 14. Find the concentration in mol dm\(^3\) if 0.25 moles are dissolved in 0.5 dm\(^3\) of solution. a) 0.5 mol dm\(^3\) b) 1 mol dm\(^3\) c) 2 mol dm\(^3\) d) 2.5 mol dm\(^3\) Answer: b) 0.5 mol dm\(^3\) Explanation: Concentration = number of moles / volume. Therefore, 0.25 moles / 0.5 dm\(^3\) = 0.5 mol dm\(^3\). 15. Determine the final volume if 0.3 moles of solute is in a 1.2 mol dm\(^3\) solution. a) 0.15 dm\(^3\) b) 0.25 dm\(^3\) c) 0.5 dm\(^3\) d) 0.6 dm\(^3\) Answer: c) 0.5 dm\(^3\) Explanation: Volume = number of moles / concentration. Therefore, 0.3 moles / 1.2 mol dm\(^3\) = 0.25 dm\(^3\). 16. Calculate the number of moles in 500 cm\(^3\) of 0.25 mol dm\(^3\) KOH solution. a) 0.125 moles b) 0.25 moles c) 0.5 moles d) 2 moles Answer: a) 0.125 moles Explanation: Number of moles = concentration × volume. Volume = 0.5 dm\(^3\), thus moles = 0.25 × 0.5 = 0.125. 17. If you have a 2 dm\(^3\) solution with a concentration of 0.75 mol dm\(^3\), how many moles are present? a) 1 mole b) 1.5 moles c) 2 moles d) 3 moles Answer: b) 1.5 moles  Explanation: Number of moles = concentration × volume. Therefore, 0.75 mol dm\(^3\) × 2 dm\ (^3\) = 1.5 moles. 18. Find the volume of solution containing 1 mole of solute if the concentration is 0.2 mol dm\(^3\). a) 2 dm\(^3\) b) 4 dm\(^3\) c) 5 dm\(^3\) d) 10 dm\(^3\) Answer: c) 5 dm\(^3\) Explanation: Volume = number of moles / concentration. Therefore, 1 mole / 0.2 mol dm\(^3\) = 5 dm\(^3\)【14:0†source】. 19. How many molecules are there in 0.3 moles of CO\(_2\)? (Avogadro’s constant = 6.02 × 10\ (^{23}\) molecules/mol) a) 1.806 × 10\(^{23}\) b) 1.204 × 10\(^{23}\) c) 3.612 × 10\(^{23}\) d) 18.06 × 10\(^{23}\) Answer: a) 1.806 × 10\(^{23}\) Explanation: Number of molecules = number of moles × Avogadro's constant = 0.3 × 6.02 × 10\ (^{23}\) = 1.806 × 10\(^{23}\). 20. Determine the number of atoms in 1 mole of H\(_2\)O molecules. a) 6.02 × 10\(^{23}\) b) 1.204 × 10\(^{24}\) c) 1.806 × 10\(^{24}\) d) 3.612 × 10\(^{24}\) Answer: c) 1.806 × 10\(^{24}\) Explanation: Each H\(_2\)O molecule contains 3 atoms. Therefore, number of atoms = 1 mole × 3 × 6.02 × 10\(^{23}\) = 1.806 × 10\(^{24}\) atoms. 21. How many moles are in 3.01 × 10\(^{23}\) molecules of O\(_2\)? a) 0.25 moles b) 0.5 moles c) 1 mole d) 1.5 moles Answer: b) 0.5 moles Explanation: Number of moles = number of molecules / Avogadro's constant = 3.01 × 10\ (^{23}\) / 6.02 × 10\(^{23}\) = 0.5 moles. 22. Find the number of moles of CaCO\(_3\) present in 1.255 × 10\(^{24}\) particles. a) 1 mole b) 1.5 moles c) 2 moles d) 2.5 moles Answer: c) 2 moles Explanation: Number of moles = number of particles / Avogadro's constant = 1.255 × 10\ (^{24}\) / 6.02 × 10\(^{23}\) = 2 moles. 26. What is the definition of concentration in chemistry? a) The amount of solute dissolved in a solvent b) The number of particles per mole of a substance c) The number of moles of solute dissolved per unit volume of solution  d) The mass of solute divided by the volume of solvent Answer: c) The number of moles of solute dissolved per unit volume of solution Explanation: Concentration is defined as the number of moles of solute per unit volume of solution in mol dm\(^3\).