Question 1

1. A student performs a measurement and records the value as 0.005080 kg. How many significant figures are present in this measurement?

A) 3B) 4C) 6D) 7

Answer

✓ Correct Answer: Option B

Explanation: Solution: Trailing zeros after a decimal point are significant, and zeros between non-zero digits are significant. Leading zeros are NOT significant. In 0.005080: - The three leading zeros (0.00) are not significant. - The digits 5, 0, 8, 0 are significant. Total = 4 significant figures.

Question 2

2. What is the molar mass of Calcium Carbonate ($CaCO_3$)? (Atomic masses: Ca = 40, C = 12, O = 16)

A) 68 g/molB) 84 g/mol 100 g/mol

Question 3

3. According to the Law of Definite Proportions, a sample of pure water ($H_2O$) will always contain Hydrogen and Oxygen in what mass ratio?

A) 1 : 8B) 2 : 1C) 1 : 16D) 8 : 1

Answer

✓ Correct Answer: Option A

Explanation: Solution: In $H_2O$, mass of Hydrogen = $2 \times 1.008 \approx 2$ units. Mass of Oxygen = 16 units. Ratio H:O = 2:16 = 1:8. This ratio remains constant regardless of the source of water.

Question 4

4. How many moles of Helium (He) atoms are contained in 20 g of Helium gas? (Atomic mass of He = 4)

A) 1 moleB) 2 molesC) 4 molesD) 5 moles

Answer

✓ Correct Answer: Option D

Explanation: Solution: Number of moles (n) = $\frac{Given mass (m)}{Molar mass (M)}$ $n = \frac{20 g}{4 g/mol} = 5 moles$.

Question 5

5. Which of the following represents the empirical formula of glucose ($C_6H_{12}O_6$)?

A) CHOB) $C_2H_4O_2$C) $CH_2O$D) $C_6H_{12}O_6$

Answer

✓ Correct Answer: Option C

Explanation: Solution: Empirical formula is the simplest whole-number ratio of atoms. Ratio C:H:O in glucose is 6:12:6. Dividing by the greatest common divisor (6), we get 1:2:1. Empirical formula = $CH_2O$.

Question 6

6. What volume does 1 mole of any ideal gas occupy at Standard Temperature and Pressure (STP, $0^\circ C$ and 1 atm)?

A) 11.2 LB) 22.4 LC) 44.8 LD) 24.0 L

Answer

✓ Correct Answer: Option B

Explanation: Solution: According to Avogadro's hypothesis, the molar volume of an ideal gas at STP (273.15 K and 1 atm) is approximately 22.4 L.

Question 7

7. Calculate the percentage of Carbon by mass in Methane ($CH_4$). (Atomic masses: C=12, H=1)

A) 75%B) 25%C) 80%D) 50%

Answer

✓ Correct Answer: Option A

Explanation: Solution: Molar mass of $CH_4 = 12 + (4 \times 1) = 16 g/mol$. $% Carbon = \left( \frac{Mass of Carbon}{Total Molar Mass} \right) \times 100$ $% Carbon = \left( \frac{12}{16} \right) \times 100 = 0.75 \times 100 = 75%$.

Question 8

8. A solution is prepared by dissolving 4 g of NaOH in enough water to make 500 mL of solution. What is the molarity? (Molar mass of NaOH = 40)

A) 0.1 MB) 0.05 MC) 0.2 MD) 0.4 M

Answer

✓ Correct Answer: Option C

Explanation: Solution: Step 1: Moles of $NaOH = \frac{4 g}{40 g/mol} = 0.1 mol$. Step 2: Volume in Liters = 500 mL = 0.5 L. Step 3: Molarity (M) = $\frac{Moles}{Volume (L)} = \frac{0.1}{0.5} = 0.2 m$.

Question 9

9. If 5 moles of $H_2$ react with excess $O_2$ according to $2H_2 + O_2 \rightarrow 2H_2O$, how many moles of $H_2O$ are produced?

A) 2.5 molesB) 10 molesC) 4 molesD) 5 moles

Answer

✓ Correct Answer: Option D

Explanation: Solution: From the balanced equation, 2 moles of $H_2$ produce 2 moles of $H_2O$. The stoichiometric ratio is 1:1. Therefore, 5 moles of $H_2$ will produce 5 moles of $H_2O$.

Question 10

10. Which subatomic particle was NOT part of Dalton's original atomic theory?

A) Atoms are indivisibleB) ElectronsC) Compounds form in fixed ratiosD) Elements consist of identical atoms

Answer

✓ Correct Answer: Option B

Explanation: Solution: Dalton's theory (1808) proposed that atoms were indivisible, hard spheres. Electrons, protons, and neutrons were discovered much later (late 19th and early 20th century). Therefore, electrons were not part of his original theory.

Accepted Answer

✓ Correct Answer: Option C

Explanation: Solution: Molar mass = $(1 \times mass of Ca) + (1 \times mass of C) + (3 \times mass of O)$ $= 40 + 12 + (3 \times 16) = 40 + 12 + 48 = 100 g/mol$.

Grade 11 Chemistry Quiz: Basic Concepts | Set 10

1. A student performs a measurement and records the value as 0.005080 kg. How many significant figures are present in this measurement?

2. What is the molar mass of Calcium Carbonate ($CaCO_3$)? (Atomic masses: Ca = 40, C = 12, O = 16)

3. According to the Law of Definite Proportions, a sample of pure water ($H_2O$) will always contain Hydrogen and Oxygen in what mass ratio?

4. How many moles of Helium (He) atoms are contained in 20 g of Helium gas? (Atomic mass of He = 4)

5. Which of the following represents the empirical formula of glucose ($C_6H_{12}O_6$)?

6. What volume does 1 mole of any ideal gas occupy at Standard Temperature and Pressure (STP, $0^\circ C$ and 1 atm)?

7. Calculate the percentage of Carbon by mass in Methane ($CH_4$). (Atomic masses: C=12, H=1)

8. A solution is prepared by dissolving 4 g of NaOH in enough water to make 500 mL of solution. What is the molarity? (Molar mass of NaOH = 40)

9. If 5 moles of $H_2$ react with excess $O_2$ according to $2H_2 + O_2 \rightarrow 2H_2O$, how many moles of $H_2O$ are produced?

10. Which subatomic particle was NOT part of Dalton's original atomic theory?