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Question (11)

QN007171

In a closed container, 5 g hydrogen reacts completely with oxygen. If 45 g water is formed, the mass of oxygen used is:

(A) 35 g
(B) 40 g
(C) 45 g
(D) 50 g

Correct Answer: B

Explanation:

Oxygen mass = 45 – 5 = 40 g.

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Question (12)

QN007172

A reaction has total reactant mass 18.6 g. If one product has mass 7.2 g and another has mass 5.4 g, the mass of the third product is:

(A) 4.0 g
(B) 5.0 g
(C) 6.0 g
(D) 7.0 g

Correct Answer: C

Explanation:

18.6 – (7.2 + 5.4) = 6.0 g.

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Question (13)

QN007173

Which setup correctly verifies the Law of Conservation of Mass for gas-producing reactions?

(A) Open beaker
(B) Open test tube
(C) Closed flask with balloon attached
(D) Open evaporating dish

Correct Answer: C

Explanation:

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Question (14)

QN007174

The mass of reactants in a reaction is 24.8 g. If only 20.1 g of products are measured in an open vessel, the most probable reason is:

(A) Law failed
(B) Balance was defective
(C) Gas escaped during reaction
(D) Matter was destroyed

Correct Answer: C

Explanation:

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Question (15)

QN007175

According to the textbook, uncertainty in a digital balance is usually:

(A) ±10 in last digit
(B) ±5 in last digit
(C) ±1 in last digit
(D) No uncertainty exists

Correct Answer: C

Explanation:

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Question (16)

QN007176

In Activity 9.2, brisk effervescence indicates formation of:

(A) Water vapour
(B) Oxygen
(C) Carbon dioxide
(D) Nitrogen

Correct Answer: C

Explanation:

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Question (17)

QN007177

If 20 g of hydrogen reacts completely with 160 g of oxygen, the mass of water formed is:

(A) 160 g
(B) 170 g
(C) 180 g
(D) 200 g

Correct Answer: C

Explanation:

Total mass = 20 + 160 = 180 g.

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Question (18)

QN007178

A student burns ethanol in an open beaker and no residue remains. This does not violate conservation of mass because:

(A) Ethanol has no mass
(B) Products escaped into air
(C) Fire destroys matter
(D) Oxygen has zero mass

Correct Answer: B

Explanation:

Gaseous products escape into the atmosphere.

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Question (19)

QN007179

In Example 9.1, the total mass of products formed was:

(A) 5.92 g
(B) 6.92 g
(C) 7.92 g
(D) 8.92 g

Correct Answer: B

Explanation:

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Question (20)

QN007180

If 4.0 g calcium carbonate reacts with 2.92 g hydrochloric acid, the total mass of reactants is:

(A) 5.92 g
(B) 6.00 g
(C) 6.92 g
(D) 7.92 g

Correct Answer: C

Explanation:

4.0 + 2.92 = 6.92 g.

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Question (11)

In a closed container, 5 g hydrogen reacts completely with oxygen. If 45 g water is formed, the mass of oxygen used is:

Explanation:

Link:

Question (12)

A reaction has total reactant mass 18.6 g. If one product has mass 7.2 g and another has mass 5.4 g, the mass of the third product is:

Explanation:

Link:

Question (13)

Which setup correctly verifies the Law of Conservation of Mass for gas-producing reactions?

Explanation:

Link:

Question (14)

The mass of reactants in a reaction is 24.8 g. If only 20.1 g of products are measured in an open vessel, the most probable reason is:

Explanation:

Link:

Question (15)

According to the textbook, uncertainty in a digital balance is usually:

Explanation:

Link:

Question (16)

In Activity 9.2, brisk effervescence indicates formation of:

Explanation:

Link:

Question (17)

If 20 g of hydrogen reacts completely with 160 g of oxygen, the mass of water formed is:

Explanation:

Link:

Question (18)

A student burns ethanol in an open beaker and no residue remains. This does not violate conservation of mass because:

Explanation:

Link:

Question (19)

In Example 9.1, the total mass of products formed was:

Explanation:

Link:

Question (20)

If 4.0 g calcium carbonate reacts with 2.92 g hydrochloric acid, the total mass of reactants is:

Explanation:

Link:

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