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Question (1)

QN0035872

Which observation most directly indicates that a solution is acidic?

(A) It turns red litmus blue
(B) It turns blue litmus red
(C) It turns phenolphthalein pink
(D) It has a pH greater than 7

Correct Answer: B

Explanation:

Acids turn blue litmus red.

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Question (2)

QN0035873

A student has only red litmus paper and three unlabelled solutions: acidic, basic and distilled water. Which sequence can identify them?

(A) Red litmus turning blue identifies the basic solution; the remaining two can be distinguished by testing the basic solution again
(B) Red litmus turning blue identifies the acidic solution
(C) All three solutions will give the same result
(D) Red litmus can identify only distilled water

Correct Answer: A

Explanation:

A basic solution turns red litmus blue.

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Question (3)

QN0035874

A solution changes phenolphthalein from colourless to pink when a few drops of another solution are added. Which conclusion is most appropriate?

(A) The added solution is definitely an acid
(B) The resulting medium is basic
(C) The resulting medium is neutral
(D) The added solution must be distilled water

Correct Answer: B

Explanation:

Phenolphthalein is pink in a basic medium.

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Question (4)

QN0035875

Equal quantities of zinc are separately treated with dilute HCl and dilute H2SO4. In both cases a gas is evolved. Which gas is expected?

(A) Oxygen
(B) Carbon dioxide
(C) Hydrogen
(D) Chlorine

Correct Answer: C

Explanation:

Acids react with metals to form a salt and hydrogen gas.

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Question (5)

QN0035876

A gas obtained by reacting zinc with dilute acid is collected in soap bubbles. A burning candle is brought near a bubble. What observation confirms the identity of the gas?

(A) The gas turns lime water milky
(B) The gas burns with a characteristic test described for hydrogen
(C) The gas extinguishes the candle without any other observation
(D) The gas changes blue litmus to red

Correct Answer: B

Explanation:

The burning test is used to identify hydrogen evolved when zinc reacts with dilute acid.

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Question (6)

QN0035877

2NaOH + Zn → Na2ZnO2 + H2. If 2 molecules of NaOH react according to this equation, how many molecules of H2 are represented?

(A) 0
(B) 1
(C) 2
(D) 4

Correct Answer: B

Explanation:

The balanced equation shows 2NaOH producing 1H2 molecule.

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Question (7)

QN0035878

A metal carbonate reacts with HCl and produces a gas that turns lime water milky. Which gas is responsible?

(A) H2
(B) O2
(C) CO2
(D) Cl2

Correct Answer: C

Explanation:

Metal carbonates and hydrogencarbonates produce CO2 with acids, and CO2 turns lime water milky.

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Question (8)

QN0035879

0.5 g Na2CO3 and 0.5 g NaHCO3 are separately treated with dilute HCl. What common gas should be expected from both test tubes?

(A) Hydrogen
(B) Carbon dioxide
(C) Oxygen
(D) Nitrogen

Correct Answer: B

Explanation:

Both metal carbonates and metal hydrogencarbonates give carbon dioxide with acids.

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Question (9)

QN0035880

If excess CO2 is passed through lime water, the initially formed insoluble calcium carbonate can change into which compound?

(A) CaO
(B) Ca(HCO3)2
(C) CaCl2
(D) CaSO4

Correct Answer: B

Explanation:

Excess CO2 reacts with calcium carbonate and water to form soluble calcium hydrogencarbonate.

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Question (10)

QN0035881

A student mixes NaOH and HCl in suitable amounts. Which ions directly combine during neutralisation?

(A) Na+ and Cl-
(B) H+ and Cl-
(C) H+ and OH-
(D) Na+ and OH-

Correct Answer: C

Explanation:

H+(aq) + OH-(aq) → H2O is the ionic form of neutralisation.

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Question (1)

Which observation most directly indicates that a solution is acidic?

Explanation:

Link:

Question (2)

A student has only red litmus paper and three unlabelled solutions: acidic, basic and distilled water. Which sequence can identify them?

Explanation:

Link:

Question (3)

A solution changes phenolphthalein from colourless to pink when a few drops of another solution are added. Which conclusion is most appropriate?

Explanation:

Link:

Question (4)

Equal quantities of zinc are separately treated with dilute HCl and dilute H2SO4. In both cases a gas is evolved. Which gas is expected?

Explanation:

Link:

Question (5)

A gas obtained by reacting zinc with dilute acid is collected in soap bubbles. A burning candle is brought near a bubble. What observation confirms the identity of the gas?

Explanation:

Link:

Question (6)

2NaOH + Zn → Na2ZnO2 + H2. If 2 molecules of NaOH react according to this equation, how many molecules of H2 are represented?

Explanation:

Link:

Question (7)

A metal carbonate reacts with HCl and produces a gas that turns lime water milky. Which gas is responsible?

Explanation:

Link:

Question (8)

0.5 g Na2CO3 and 0.5 g NaHCO3 are separately treated with dilute HCl. What common gas should be expected from both test tubes?

Explanation:

Link:

Question (9)

If excess CO2 is passed through lime water, the initially formed insoluble calcium carbonate can change into which compound?

Explanation:

Link:

Question (10)

A student mixes NaOH and HCl in suitable amounts. Which ions directly combine during neutralisation?

Explanation:

Link:

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