Question 1

1. A jewelry designer measures the mass of a pure gold ring as 19.700 g. How many significant figures are present in this measurement?

A) 3B) 4C) 5D) 2

Answer

✓ Correct Answer: Option C

Explanation: Explanation: According to the rules for significant figures, trailing zeros in a number containing an explicit decimal point are significant. Therefore, all five digits (1, 9, 7, 0, 0) are significant.

Question 2

2. An environmentalist analyzes water samples from a local river and a distant glacier. Both samples show that hydrogen and oxygen are present in a mass ratio of 1:8. This observation supports which law?

A) Law of Conservation of MassB) Law of Definite Proportions

Question 3

3. A chef uses 46 g of sodium (atomic mass = 23 u) in a specialized chemical cooking process. How many moles of sodium atoms did the chef use?

A) 2.0 molB) 1.0 molC) 0.5 molD) 46 mol

Answer

✓ Correct Answer: Option A

Explanation: Solution: $$Number of moles (n) = \frac{Given mass (w)}{Molar mass (M)}$$ $$n = \frac{46g}{23 g/mol} = 2.0 mol$$

Question 4

4. A weather balloon is filled with 4.0 g of Helium gas (atomic mass = 4 u). What volume will this gas occupy at STP (Standard Temperature and Pressure)?

A) 11.2 LB) 44.8 LC) 2.24 LD) 22.4 L

Answer

✓ Correct Answer: Option D

Explanation: Solution: $$Moles of He = \frac{4.0g}{4 g/mol} = 1 mol$$ Since 1 mole of any ideal gas occupies precisely 22.4 L volume space at standard conditions (STP), the final value is 22.4 L.

Question 5

5. A laboratory produces a cleaning agent by dissolving 40 g of NaOH (molar mass = 40 g/mol) in enough water to make 500 mL of solution. What is the molarity (M) of this solution?

A) 1.0 MB) 2.0 MC) 0.5 MD) 4.0\text; M}

Answer

✓ Correct Answer: Option B

Explanation: Solution: $$Moles of NaOH = \frac{40g}{40 g/mol} = 1 mol$$ $$Volume in Liters = \frac{500 mL}{1000} = 0.5 L$$ $$Molarity (M) = \frac{moles of solute}{Volume of solution in L} = \frac{1}{0.5} = 2.0m$$

Question 6

6. An industrial process requires the reaction of 12 g of Magnesium with 16 g of Oxygen to form Magnesium Oxide (MgO). If the Law of Conservation of Mass holds perfectly, what is the expected mass of the product?

A) 4 gB) 24 gC) 28 gD) 56 g

Answer

✓ Correct Answer: Option C

Explanation: Explanation: According to the Law of Conservation of Mass, the combined mass of the reactants must precisely equal the net total mass of the generated products. $Total Product Mass = 12 g (Mg) + 16 g (O) = 28g.$

Question 7

7. A molecule used in botanical research has the molecular formula $C_6H_{12}O_6$. What is its empirical formula?

A) $CH_2O$B) CHOC) $C_2H_4O_2$D) $CH_3O$

Answer

✓ Correct Answer: Option A

Explanation: Solution: The empirical formula tracks the lowest, simplest whole-number ratio of individual atoms inside a compound. Atomic ratio C:H:O = 6:12:6. Dividing through by the lowest factor (6) gives: 1:2:1. $$Empirical Formula = CH_2O.$$

Question 8

8. A scientist finds that 1 mole of a gas contains approximately $6.022 \times 10^{23}$ molecules. This constant quantitative value is universally known as:

A) Planck's ConstantB) Avogadro's NumberC) Boltzmann ConstantD) Rydberg Constant

Answer

✓ Correct Answer: Option B

Explanation: Explanation: The value $6.022 \times 10^{23}$ denotes **Avogadro's Number** ($N_A$). It serves as the standard counting index baseline containing fundamental entities per single mole of a substance.

Question 9

9. In a fertilizer plant, a technician mixes 10 g of urea in 90 g of water. What is the mass percent of urea in the solution?

A) 90%B) 11.1%C) 100%D) 10%

Answer

✓ Correct Answer: Option D

Explanation: Solution: $$Mass % of solute = \left( \frac{Mass of solute}{Mass of solute + Mass of solvent} \right) \times 100$$ $$Mass % of urea = \left( \frac{10}{10 + 90} \right) \times 100 = \left( \frac{10}{100} \right) \times 100 = 10%.$$

Question 10

10. Which of the following configurations represents a heterogeneous mixture in a real-world setting?

A) A sugar solution in waterB) Filtered airC) A mixture of sand and iron filingsD) Pure distilled water

Answer

✓ Correct Answer: Option C

Explanation: Explanation: A heterogeneous mixture maintains a non-uniform composition throughout its structure where components can be physically distinguished. Sand and iron filings do not intermix uniformly and can be parsed apart easily via common mechanical tools like a magnet.

Accepted Answer

✓ Correct Answer: Option B

Explanation: Explanation: The Law of Definite Proportions (Proust's Law) states that a given chemical compound always contains its component elements combined together in a fixed, constant ratio by mass, completely independent of its source or method of preparation.

Grade 11 : Chemistry - Basic Concepts (Set 2)

1. A jewelry designer measures the mass of a pure gold ring as 19.700 g. How many significant figures are present in this measurement?

2. An environmentalist analyzes water samples from a local river and a distant glacier. Both samples show that hydrogen and oxygen are present in a mass ratio of 1:8. This observation supports which law?

3. A chef uses 46 g of sodium (atomic mass = 23 u) in a specialized chemical cooking process. How many moles of sodium atoms did the chef use?

4. A weather balloon is filled with 4.0 g of Helium gas (atomic mass = 4 u). What volume will this gas occupy at STP (Standard Temperature and Pressure)?

5. A laboratory produces a cleaning agent by dissolving 40 g of NaOH (molar mass = 40 g/mol) in enough water to make 500 mL of solution. What is the molarity (M) of this solution?

6. An industrial process requires the reaction of 12 g of Magnesium with 16 g of Oxygen to form Magnesium Oxide (MgO). If the Law of Conservation of Mass holds perfectly, what is the expected mass of the product?

7. A molecule used in botanical research has the molecular formula $C_6H_{12}O_6$. What is its empirical formula?

8. A scientist finds that 1 mole of a gas contains approximately $6.022 \times 10^{23}$ molecules. This constant quantitative value is universally known as:

9. In a fertilizer plant, a technician mixes 10 g of urea in 90 g of water. What is the mass percent of urea in the solution?

10. Which of the following configurations represents a heterogeneous mixture in a real-world setting?