IGCSE Chemistry Paper-1: Specimen Questions with Answers 75 - 77 of 99

Passage

In the below questions. Complete the following puzzle.

Complete the puzzle above

Complete the Puzzle Above

Question number: 75 (6 of 6 Based on Passage) Show Passage

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Question

ACROSS: At position 47, a gas with atomic number 3.

Choices

Choice (4)Response

a.

Neon

b.

Helium

c.

Lithium

d.

Argon

Answer

c.

Explanation

Lithium is a chemical element with symbol Li and atomic number 3. It is a soft, silver-white metal belonging to the alkali metal group of chemical elements. Under standard conditions it is the lightest metal and the least dense solid element.

Completed Puzle given in the question

Completed Puzle Given in the Question

Question number: 76

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Question

What is the Chemical formula and chemical name of vinegar?

Choices

Choice (4)Response

a.

Carbonic acid - H₂ CO₃

b.

Acetic acid - CH₃COOH

c.

Lactic acid - CH₃CH (OH) COOH

d.

Nitric Acid - HNO₃

Answer

b.

Explanation

Acetic acid has a chemical formula CH3COOH. Vinegar is roughly 3–9 % acetic acid by volume, making acetic acid the main component of vinegar apart from water. Vinegar is now mainly used as a cooking ingredient. Historically, as the most easily available mild acid, it had a great variety of industrial, medical and domestic uses, some of which (such as its use as a general household cleanser) are still promoted today.

Question number: 77

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Question

A solution of NaOH was taken in a test tube and phenolphthalein was added to it. The solution turned pink by doing so. Now HCl is added to it and the pink colour disappeared.

What reaction possibly would have taken place?

Adding Dilute HCl to NaOH

Adding Dilute HCl to NaOH

Choices

Choice (4)Response

a.

Double displacement

b.

Reduction

c.

Decomposition

d.

Neutralization

Answer

d.

Explanation

A neutralization reaction is when an acid and a base react to form water and a salt and involves the combination of H+ ions and OH- ions to generate water. The neutralization of a strong acid and strong base has a pH equal to 7.

This experiment shows that the addition of HCl destroys the alkaline nature of NaOH. On the other hand the addition of NaOH solution destroys the acidic nature of HCl. i. e. both NaOH and HCl appear to cancel the effect of each other.

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