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Chemistry MCQ & Objective Questions

Chemistry is a vital subject in the academic journey of students, especially for those preparing for school exams and competitive tests. Mastering Chemistry concepts not only enhances your understanding but also boosts your confidence in tackling objective questions. Practicing MCQs and objective questions is crucial for scoring better, as it helps in identifying important questions and reinforces key concepts essential for exam preparation.

What You Will Practise Here

Fundamental concepts of Atomic Structure
Periodic Table trends and properties
Chemical Bonding and Molecular Structure
Stoichiometry and Chemical Calculations
Acids, Bases, and Salts: Definitions and Properties
Thermodynamics and Chemical Equilibrium
Organic Chemistry: Functional Groups and Reactions

Exam Relevance

Chemistry is a core subject in various examinations, including CBSE, State Boards, NEET, and JEE. Questions often focus on conceptual understanding and application, with patterns ranging from direct MCQs to scenario-based questions. Familiarity with important Chemistry questions for exams can significantly enhance your performance, as many competitive exams emphasize problem-solving and analytical skills.

Common Mistakes Students Make

Misunderstanding the periodic trends and their implications.
Confusing different types of chemical bonds and their properties.
Errors in stoichiometric calculations due to improper unit conversions.
Overlooking the significance of reaction mechanisms in organic chemistry.
Neglecting to practice diagrams and representations of molecular structures.

FAQs

Question: What are the best ways to prepare for Chemistry MCQs?
Answer: Regular practice of MCQs, understanding key concepts, and reviewing previous years' question papers are effective strategies.

Question: How can I improve my speed in solving Chemistry objective questions?
Answer: Time yourself while practicing and focus on mastering the fundamental concepts to enhance your speed and accuracy.

Don't wait any longer! Start solving practice MCQs today to test your understanding and solidify your Chemistry knowledge. Your success in exams is just a question away!

Acids, Bases & Salts Atomic Structure Chemical Reactions Matter & States Metals & Non-Metals Organic Chemistry Basics

Q. How many unpaired electrons are present in a nitrogen atom? (2023)

A. 1
B. 2
C. 3
D. 4

Solution

Nitrogen has an atomic number of 7, with the electron configuration of 1s² 2s² 2p³, resulting in 3 unpaired electrons in the 2p subshell.

Correct Answer: C — 3

Q. If 10 g of a substance reacts completely with 20 g of another substance, what is the total mass of the products formed? (2020)

A. 30 g
B. 20 g
C. 10 g
D. 40 g

Solution

According to the law of conservation of mass, the total mass of the products is equal to the total mass of the reactants, which is 10 g + 20 g = 30 g.

Correct Answer: A — 30 g

Q. If 10 grams of NaCl is dissolved in 500 mL of water, what is the concentration in grams per liter? (2022)

A. 10 g/L
B. 20 g/L
C. 5 g/L
D. 15 g/L

Solution

Concentration = mass/volume = 10 g / 0.5 L = 20 g/L.

Correct Answer: A — 10 g/L

Q. If the pH of a solution is 11, what is the concentration of hydroxide ions [OH-] in the solution?

A. 1 x 10^-3 M
B. 1 x 10^-11 M
C. 1 x 10^-2 M
D. 1 x 10^-14 M

Solution

pOH = 14 - pH = 3, [OH-] = 10^-3 M.

Correct Answer: C — 1 x 10^-2 M

Q. In a double displacement reaction, which of the following pairs will react? (2021)

A. NaCl + AgNO3
B. HCl + NaOH
C. CaCl2 + Na2SO4
D. All of the above

Solution

All the given pairs can undergo double displacement reactions.

Correct Answer: D — All of the above

Q. In a reaction, 2 moles of hydrogen gas react with 1 mole of oxygen gas to form water. How many grams of water are produced? (2020)

A. 18 g
B. 36 g
C. 9 g
D. 27 g

Solution

2H2 + O2 → 2H2O. 1 mole of water weighs 18 g, so 2 moles produce 36 g. Thus, 18 g of water is produced from 1 mole of O2.

Correct Answer: A — 18 g

Q. In a reaction, 2 moles of hydrogen react with 1 mole of oxygen to form water. How many grams of water are produced? (2020)

A. 18 g
B. 36 g
C. 9 g
D. 27 g

Solution

2 moles of H2 and 1 mole of O2 produce 2 moles of H2O. The molar mass of water is 18 g/mol, so 2 moles produce 36 g.

Correct Answer: A — 18 g

Q. In the reaction 2Fe + 3Cl2 → 2FeCl3, how many moles of FeCl3 are produced from 4 moles of Fe? (2021)

A. 2 moles
B. 4 moles
C. 6 moles
D. 8 moles

Solution

From 2 moles of Fe, 2 moles of FeCl3 are produced. Therefore, from 4 moles of Fe, 4 moles of FeCl3 are produced.

Correct Answer: B — 4 moles

Q. In the reaction 2Na + Cl2 → 2NaCl, how many grams of NaCl can be produced from 2 moles of Na? (2021)

A. 58.5 g
B. 117 g
C. 29.25 g
D. 146 g

Solution

2 moles of Na produce 2 moles of NaCl. Molar mass of NaCl = 58.5 g/mol. Therefore, 2 moles of NaCl = 2 × 58.5 g = 117 g.

Correct Answer: B — 117 g

Q. In the reaction 2Na + Cl2 → 2NaCl, how many grams of sodium chloride are produced from 4 moles of sodium? (2023)

A. 236 g
B. 118 g
C. 472 g
D. 59 g

Solution

4 moles of Na produce 4 moles of NaCl. Molar mass of NaCl = 58.5 g/mol. Therefore, 4 × 58.5 = 236 g.

Correct Answer: A — 236 g

Q. In the reaction 2Na + Cl2 → 2NaCl, how many moles of NaCl are produced from 4 moles of Na? (2023)

A. 2 moles
B. 4 moles
C. 6 moles
D. 8 moles

Solution

From 2 moles of Na, 2 moles of NaCl are produced. Therefore, from 4 moles of Na, 4 moles of NaCl are produced.

Correct Answer: B — 4 moles

Q. What happens to the volume of a gas when it is compressed? (2022)

A. It increases
B. It decreases
C. It remains the same
D. It becomes solid

Solution

When a gas is compressed, the volume decreases because the particles are forced closer together.

Correct Answer: B — It decreases

Q. What is the balanced equation for the combustion of propane (C3H8)? (2021)

A. C3H8 + 5O2 → 3CO2 + 4H2O
B. C3H8 + 4O2 → 3CO2 + 2H2O
C. C3H8 + 3O2 → 3CO + 4H2O
D. C3H8 + 2O2 → 3CO2 + 2H2O

Solution

The balanced equation for the combustion of propane is C3H8 + 5O2 → 3CO2 + 4H2O.

Correct Answer: A — C3H8 + 5O2 → 3CO2 + 4H2O

Q. What is the chemical formula for sulfuric acid? (2023)

A. H2SO4
B. H2SO3
C. H2S
D. SO2

Solution

The chemical formula for sulfuric acid is H2SO4, which consists of two hydrogen atoms, one sulfur atom, and four oxygen atoms.

Correct Answer: A — H2SO4

Q. What is the coefficient of O2 when balancing the equation: C4H10 + O2 → CO2 + H2O? (2023)

A. 5
B. 6
C. 7
D. 8

Solution

The balanced equation is C4H10 + 6O2 → 4CO2 + 5H2O, so the coefficient of O2 is 6.

Correct Answer: B — 6

Q. What is the conjugate base of sulfuric acid (H2SO4)?

A. HSO4-
B. SO4^2-
C. H3O+
D. None of the above

Solution

The conjugate base of sulfuric acid (H2SO4) is HSO4-.

Correct Answer: B — SO4^2-

Q. What is the effect of adding a base to a solution of a weak acid?

A. Increase in pH
B. Decrease in pH
C. No change in pH
D. Increase in temperature

Solution

Adding a base to a weak acid will neutralize some of the acid, increasing the pH.

Correct Answer: A — Increase in pH

Q. What is the effect of adding a base to a solution of hydrochloric acid?

A. Increase in pH
B. Decrease in pH
C. No effect
D. Formation of salt only

Solution

Adding a base to hydrochloric acid will neutralize it, resulting in an increase in pH.

Correct Answer: A — Increase in pH

Q. What is the effect of adding a base to an acidic solution?

A. Increase in pH
B. Decrease in pH
C. No effect
D. Formation of salt only

Solution

Adding a base to an acidic solution increases the pH, making it less acidic.

Correct Answer: A — Increase in pH

Q. What is the effect of adding a strong acid to a solution of a weak base?

A. Increase in pH
B. Decrease in pH
C. No effect
D. Increase in conductivity

Solution

Adding a strong acid to a weak base will decrease the pH of the solution.

Correct Answer: B — Decrease in pH

Q. What is the electron configuration of a chlorine atom (atomic number 17)? (2020)

A. 1s² 2s² 2p⁶ 3s² 3p⁵
B. 1s² 2s² 2p⁶ 3s² 3p⁶
C. 1s² 2s² 2p⁶ 3s² 3p⁴
D. 1s² 2s² 2p⁶ 3s² 3d⁵

Solution

The electron configuration of chlorine is 1s² 2s² 2p⁶ 3s² 3p⁵, filling up to the 3p subshell.

Correct Answer: A — 1s² 2s² 2p⁶ 3s² 3p⁵

Q. What is the electron configuration of a neutral carbon atom? (2022)

A. 1s² 2s² 2p²
B. 1s² 2s² 2p⁶
C. 1s² 2s² 2p⁴
D. 1s² 2s² 2p³

Solution

Carbon has an atomic number of 6, and its electron configuration is 1s² 2s² 2p².

Correct Answer: A — 1s² 2s² 2p²

Q. What is the electron configuration of an oxygen atom? (2021)

A. 1s² 2s² 2p⁴
B. 1s² 2s² 2p²
C. 1s² 2s² 2p⁶
D. 1s² 2s² 2p³

Solution

Oxygen has 8 electrons, and its electron configuration is 1s² 2s² 2p⁴.

Correct Answer: A — 1s² 2s² 2p⁴

Q. What is the empirical formula of a compound with a molecular formula C6H12? (2021)

A. CH
B. C2H4
C. C3H6
D. C6H12

Solution

The empirical formula is obtained by dividing the subscripts by the greatest common divisor, which is 2. Thus, C6H12 becomes C3H6.

Correct Answer: B — C2H4

Q. What is the empirical formula of a compound with the molecular formula C6H12? (2021)

A. CH
B. C2H4
C. C3H6
D. C6H12

Solution

The empirical formula is obtained by dividing the subscripts by the greatest common divisor, which is 2. Thus, C6H12 becomes C3H6.

Correct Answer: B — C2H4

Q. What is the formula for calculating the concentration of hydrogen ions in a solution from its pH?

A. [H+] = 10^-pH
B. [H+] = pH/10
C. [H+] = 10^pH
D. [H+] = pH^10

Solution

The concentration of hydrogen ions is calculated using [H+] = 10^-pH.

Correct Answer: A — [H+] = 10^-pH

Q. What is the formula for calculating the concentration of hydrogen ions in a solution with a pH of 5?

A. 1 x 10^-5 M
B. 1 x 10^-7 M
C. 1 x 10^-9 M
D. 1 x 10^-3 M

Solution

The concentration of hydrogen ions is calculated as [H+] = 10^-pH = 10^-5 M.

Correct Answer: A — 1 x 10^-5 M

Q. What is the formula for calculating the normality of a solution?

A. N = M x n
B. N = M / n
C. N = M + n
D. N = M - n

Solution

Normality (N) is calculated as the molarity (M) multiplied by the number of equivalents (n).

Correct Answer: A — N = M x n

Q. What is the formula for calculating the pH of a solution?

A. pH = log[H+]
B. pH = -log[H+]
C. pH = [H+]
D. pH = 14 - pOH

Solution

The formula for calculating pH is pH = -log[H+].

Correct Answer: B — pH = -log[H+]

Q. What is the IUPAC name for CH3-CH2-COOH?

A. Propanoic acid
B. Butanoic acid
C. Acetic acid
D. Methanoic acid

Solution

The IUPAC name for CH3-CH2-COOH is propanoic acid, as it has three carbon atoms in the longest chain.

Correct Answer: A — Propanoic acid

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