Some Basic Concepts Of Chemistry Multiple Choice Questions

Some Basic Concepts Of Chemistry Multiple Choice Questions

Question 1. The number of significant figures in 0.0450 is

1. 3
2. 4
3. 5
4. 2

Answer: 1. 3

Question 2. The number of significant figures in 2.345 x 10⁴ is

1. 1
2. 2
3. 3
4. 4

Answer: 4. 4

Question 3. Which of the following is/are mixtures?

1. 20-carat gold
2. Iodised salt
3. Milk
4. Distilled water

Answer:

1. 20 carat gold
2. Iodised salt
3. Milk

Question 4. 1 mol of oxygen atoms represents

1. 16 g of oxygen
2. 6.022 x 10²³ atoms of oxygen
3. 22.7 L of oxygen at stp
4. 32 g of oxygen

Answer:

1. 16 g of oxygen
2. 6.022 x 10²³ atoms of oxygen
3. 22.7 L of oxygen at stp

Question 5. Which of the following is/are heteroatomic molecules?

1. CH₄
2. H₂O
3. O₂
4. Br₂

Answer:

1. CH₂
2. H₂O

Question 6. The sum of the atomic masses of two elements is 407.8 u. If one of them is mercury, the other element is

1. Silver
2. Tin
3. Lead
4. Bismuth

Answer: 3. Lead

Question 7. Which of the following represent/s 1 mol?

1. 11.2 L of a gas at stp
2. 18 g of water
3. 23 g of sodium
4. 100 g of calcium carbonate

Answer:

2. 18 g of water

3. 23 g of sodium

4. 100 g of calcium carbonate

Question 8. The molarity of a solution containing 2.8 g of KOH in 200 mL of water is

1. 2.8 M
2. 0.5 M
3. 0.28M
4. 0.25M

Answer: 4. 0.25M

Question 9. Which of the following contains the most molecules?

1. 1 g of H₂S
2. 1 g of H₂
3. 1 g of H₂O
4. 1 g of CH₄

Answer: 2. 1 g of H₂

Question 10. Which of the following has the least weight?

1. 1 mol of water
2. 3 gram-molecules of Cu₂
3. 0.2 mol of sucrose
4. 1 gram-atom of Na

Answer: 1. 1 mol of water

Question 11. Which of the following will have the least volume at stp?

1. 5g of HCl
2. 5g of HBr
3. 5g of HF
4. 5g of HI

Answer: 4. 5g of HI

Question 12. According to Dalton’s atomic theory’, which of the following happens during a reaction?

1. Atoms are destroyed.
2. Atoms are created.
3. Atoms are rearranged.
4. Atoms are converted into other kinds of atoms.

Answer: 3. Atoms are rearranged.

Question 13. 1 gram-atom of nitrogen weighs

1. 28g
2. 14 g
3. 7g
4. 56g

Answer: 1. 28g

Question 14. The volume occupied by 1 mol of hydrogen is

1. 2.24 L
2. 11.2 L
3. 224 L
4. 22.7 L

Answer: 4. 22.7 L

Question 15. The isotopes of an element differ in

1. The number of electrons
2. The number of protons
3. The number of neutrons
4. The number of electrons + protons

Answer: 3. The number of neutrons

Question 16. The mass of a silver atom is

1. 187.8g
2. 6.022 x 10²³ g/m
3. \(\frac{107.87}{6.022 \times 10^{23}} g\)
4. 3.01 x 10²³ g

Answer: 3. \(\frac{107.87}{6.022 \times 10^{23}} g\)

Question 17. The number of grams of oxygen in 0.10 mol of Na₂CO₄ -10H₂O is

1. 20.8
2. 16
3. 32
4. 8

Answer: 1. 20.8

Question 18. 1 mol each of ammonia and oxygen are made to react according to the following equation.

⇒ \(4 \mathrm{NH}_3+5 \mathrm{O}_2 \longrightarrow 4 \mathrm{NO}+6 \mathrm{H}_2 \mathrm{O}\)

Which of the statements below is/are true?

1. 1 mol of H₂O is produced.
2. 1 mol of NO is produced.
3. All the ammonia is consumed.
4. All the oxygen is consumed.

Answer: 4. All the oxygen is consumed.