Question 1

Which of the following is a characteristic feature of a chemical reaction?

Accepted Answer

A chemical reaction involves breaking old bonds and forming new substances with different properties, distinguishing it from physical changes.

Question 2

In the reaction: 2H₂ + O₂ → 2H₂O, how many moles of water are produced from 4 moles of hydrogen gas?

Accepted Answer

From the balanced equation, 2 moles of H₂ produces 2 moles of H₂O; therefore, 4 moles of H₂ produces 4 moles of H₂O.

Question 3

Which type of chemical reaction occurs when a single compound breaks down into two or more simpler substances?

Accepted Answer

A decomposition reaction is defined as the breaking down of one compound into two or more simpler substances.

Question 4

When iron reacts with oxygen to form iron oxide, this type of reaction is classified as:

Accepted Answer

Two or more substances (iron and oxygen) combine to form a single new substance (iron oxide), which defines a combination reaction.

Question 5

When magnesium ribbon burns in oxygen, it forms magnesium oxide. This is an example of which type of chemical reaction?

Accepted Answer

Magnesium and oxygen combine to form a single product (magnesium oxide), which is the defining characteristic of a combination reaction.

Question 6

When calcium carbonate is heated strongly, it decomposes into calcium oxide and carbon dioxide. What is the balanced chemical equation for this reaction?

Accepted Answer

One mole of calcium carbonate decomposes to produce one mole each of calcium oxide and carbon dioxide with balanced atoms on both sides.

Question 7

In the reaction: Zn + CuSO₄ → ZnSO₄ + Cu, which substance is being oxidized?

Accepted Answer

Zinc loses electrons and goes from 0 oxidation state to +2 in ZnSO₄, which is oxidation.

Question 8

When silver nitrate solution reacts with sodium chloride solution, a white precipitate forms. This is an example of which type of chemical reaction?

Accepted Answer

Two compounds exchange ions to form silver chloride (precipitate) and sodium nitrate, which is characteristic of double displacement reactions.

Question 9

Which of the following is a sign that a chemical reaction has occurred?

Accepted Answer

Observable signs of chemical reactions include formation of gas, change in color, formation of precipitate, and change in temperature, indicating new substances have formed.

Question 10

When 2.3 g of sodium reacts with oxygen, which type of chemical reaction occurs and what is the primary product formed?

Accepted Answer

Sodium combines with oxygen in a combination reaction to form sodium peroxide (Na₂O₂) as the primary product, as sodium burns in excess oxygen.

Question 11

In a neutralization reaction between 40 mL of 1 M HCl and 20 mL of 2 M NaOH, which statement correctly describes the outcome?

Accepted Answer

HCl (0.04 mol) reacts with NaOH (0.04 mol) in a 1:1 ratio; since only 0.04 mol of NaOH is available but 0.04 mol of HCl is present, NaOH is the limiting reagent and 0.04 mol of NaCl forms.

Question 12

When lead nitrate solution is mixed with potassium iodide solution, a yellow precipitate forms. What type of reaction is this and what is the precipitate?

Accepted Answer

This is a double displacement reaction where Pb²⁺ and I⁻ ions combine to form yellow lead iodide (PbI₂) precipitate, insoluble in water.

Agniveer Army GD Chemical Reactions

Chemical Reactions — Practice Questions