Grade 11 : Chemistry - Basic Concepts (Set 1) | Concept of Maths

Question 1

1. How many significant figures are present in the measurement $0.0025\text{ g}$?

A) 1

B) 2

C) 3

D) 4

Answer

Correct Answer: B

Explanation: Leading zeros acting as placeholders before the first non-zero digit are not significant. Only the non-zero integer digits $2$ and $5$ are significant. Thus, the total count is $2$.

Question 2

2. What is the standard scientific notation expression representing the number $450,000$?

A) $4.5 \times 10^5$

B) $45 \times 10^4$

C) $4.5 \times 10^{-5}$

D) $0.45 \times 10^6$

Answer

Correct Answer: A

Explanation: Shift the reference decimal point $5$ positions leftward: $450,000.0 \rightarrow 4.5$. Because the positional progression tracks leftward, the tracking exponential exponent factor is positive: $4.5 \times 10^5$.

Question 3

3. Calculate the standard molar mass of Methane ($CH_4$). (Atomic mass constants: $C = 12.01$, $H = 1.008$)

A) $13.018\text{ g/mol}$

B) $14.04\text{ g/mol}$

C) $16.04\text{ g/mol}$

D) $18.02\text{ g/mol}$

Answer

Correct Answer: C

Solution: $$\text{Molar Mass} = 1 \times (12.01) + 4 \times (1.008) = 12.01 + 4.032 = 16.042\text{ g/mol}$$ Rounding cleanly down to two decimal places yields $16.04\text{ g/mol}$.

Question 4

4. One mole of water ($H_2O$) molecules contains precisely how many individual molecules?

Question 5

5. Which of the following units defines the official SI base unit tracking the amount of substance?

A) Kilogram

B) Gram

C) Liter

D) Mole

Answer

Correct Answer: D

Explanation: The International System of Units (SI) defines the **mole** (symbol: mol) as the base foundational measurement unit for aggregate amount of substance.

Question 6

6. What is the net mass of $2.0\text{ moles}$ of Carbon Dioxide ($CO_2$)? (Molar mass of $CO_2 = 44\text{ g/mol}$)

A) $44\text{ g}$

B) $88\text{ g}$

C) $22\text{ g}$

D) $100\text{ g}$

Answer

Correct Answer: B

Solution: $$\text{Mass} = \text{moles} \times \text{molar mass} = 2.0\text{ mol} \times 44\text{ g/mol} = 88\text{ g.}$$

Question 7

7. Calculate the mass percentage of Oxygen inside standard Water ($H_2O$). (Molar mass references: $H_2O = 18\text{ g/mol}$, $O = 16\text{ g/mol}$)

A) $88.89\%$

B) $11.11\%$

C) $50.00\%$

D) $16.00\%$

Answer

Correct Answer: A

Solution: $$\text{Mass } \% = \left( \frac{\text{Mass of O component}}{\text{Total molar mass of } H_2O} \right) \times 100 = \left( \frac{16}{18} \right) \times 100 \approx 88.89\%.$$

Question 8

8. Which pioneering chemical scientist is credited with establishing the Law of Conservation of Mass?

A) John Dalton

B) Joseph Proust

C) Antoine Lavoisier

D) Gay-Lussac

Answer

Correct Answer: C

Explanation: Antoine Lavoisier formulated the fundamental Law of Conservation of Mass, establishing experimentally that mass is neither created nor destroyed during the course of an isolated chemical reaction.

Question 9

9. What is the empirical formula representation of Benzene ($C_6H_6$)?

A) $C_2H_2$

B) $CH$

C) $C_3H_3$

D) $C_6H_6$

Answer

Correct Answer: B

Explanation: The empirical formula profiles the simplest, irreducible whole-number integer ratio of atoms. For molecular formula $C_6H_6$, the subscript ratio $6:6$ reduces down structurally to $1:1$, yielding formula $CH$.

Question 10

10. Molarity ($M$) concentration is formally defined as the total number of moles of solute dissolved within:

A) 1 Liter of solution

B) 1 Kilogram of solvent

C) 1 Liter of solvent

D) 1 mole of solute

Answer

Correct Answer: A

Explanation: Molarity is a volumetric concentration parameter defined strictly as the absolute number of moles of solute contained per single Liter ($1\text{ L}$) of the total combined volumetric solution space.

Accepted Answer

Correct Answer: A

Explanation: By chemical definition, $1$ mole of any pure elementary substance contains Avogadro's constant number of particles: $N_A = 6.022 \times 10^{23}$.

Grade 11 : Chemistry - Basic Concepts (Set 1) | Concept of Maths