Chemistry Questions

Found 12 practice questions from various admission tests.

1. What is the pH of pure water at 25°C?

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A. 0

B. 7✓ Correct

C. 14

D. 1

Explanation: Pure water has equal concentrations of H⁺ and OH⁻ ions, giving pH = 7.

2. Which gas is evolved when zinc reacts with dilute HCl?

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A. Oxygen

B. Chlorine

C. Hydrogen✓ Correct

D. Nitrogen

Explanation: Zn + 2HCl → ZnCl₂ + H₂↑. Hydrogen gas is evolved.

3. The number of electrons in the outermost shell of Carbon is:

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A. 2

B. 4✓ Correct

C. 6

D. 8

Explanation: Carbon (Z=6) has electronic configuration 2,4. So 4 electrons in the outermost shell.

4. Which of the following is an exothermic reaction?

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A. Photosynthesis

B. Electrolysis

C. Combustion of methane✓ Correct

D. Thermal decomposition

Explanation: Combustion reactions release heat energy, making them exothermic.

5. Avogadro's number is:

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A. 6.022 × 10²³✓ Correct

B. 6.022 × 10²²

C. 6.022 × 10²⁴

D. 3.011 × 10²³

Explanation: One mole of any substance contains 6.022 × 10²³ particles.

6. Which element has the highest electronegativity?

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A. Oxygen

B. Nitrogen

C. Fluorine✓ Correct

D. Chlorine

Explanation: Fluorine has the highest electronegativity (3.98) on the Pauling scale.

7. The IUPAC name of CH₃CHO is:

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A. Methanol

B. Ethanal✓ Correct

C. Propanal

D. Ethanol

Explanation: CH₃CHO is acetaldehyde, and its IUPAC name is ethanal.

8. Which type of bond is present in NaCl?

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A. Covalent

B. Ionic✓ Correct

C. Metallic

D. Hydrogen

Explanation: NaCl is formed by transfer of electron from Na to Cl, creating ionic bonds.

9. What is the hybridization of carbon in CH₄?

BUET Engineering Mock Test

A. sp

B. sp²

C. sp³✓ Correct

D. sp³d

Explanation: Carbon in methane (CH₄) forms 4 sigma bonds with no lone pairs, leading to sp³ hybridization.

10. Which of the following is an intensive property?

BUET Engineering Mock Test

A. Mass

B. Volume

C. Density✓ Correct

D. Internal Energy

Explanation: An intensive property does not depend on the amount of substance. Density is mass/volume and remains constant regardless of quantity.

11. Which of the following is an electrophile?

DU A-Unit (Science) Mock

A. NH₃

B. H₂O

C. BF₃✓ Correct

D. CN⁻

Explanation: BF₃ is an electron-deficient molecule and acts as a Lewis acid (electrophile).

12. What is the oxidation number of Cr in K₂Cr₂O₇?

RU Science Unit Mock

A. +3

B. +6✓ Correct

C. +7

D. +12

Explanation: Let oxidation state of Cr be x. 2(+1) + 2x + 7(-2) = 0. 2x = +12. x = +6.