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Question (21)

QN002751

A mobile phone contains many elements including aluminium, lithium, and cobalt. This shows that elements are

(A) useless in technology
(B) used in manufacturing devices
(C) only found in liquids
(D) always gases

Correct Answer: B

Explanation:

Many elements are used in electronic devices.

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Question (22)

QN002752

Which of the following cannot be separated by physical methods?

(A) Sand and water
(B) Sugar solution
(C) Iron and sulfur mixture
(D) Water into hydrogen and oxygen

Correct Answer: D

Explanation:

Water is a compound and requires chemical methods for separation.

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Question (23)

QN002753

Sodium chloride is formed from sodium and chlorine in the ratio

(A) 1 : 2
(B) 2 : 1
(C) 1 : 1
(D) 3 : 1

Correct Answer: C

Explanation:

Sodium chloride contains sodium and chlorine in 1:1 ratio.

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Question (24)

QN002754

Sodium chloride is commonly known as

(A) baking soda
(B) washing soda
(C) common salt
(D) quick lime

Correct Answer: C

Explanation:

Sodium chloride is common salt.

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Question (25)

QN002755

Which observation proves that sugar is not an element?

(A) It dissolves in water
(B) It decomposes into carbon and water on heating
(C) It tastes sweet
(D) It forms crystals

Correct Answer: B

Explanation:

Sugar breaks into simpler substances on heating.

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Question (26)

QN002756

On heating sugar strongly, the black residue left behind is mainly

(A) sulfur
(B) oxygen
(C) charcoal
(D) iron

Correct Answer: C

Explanation:

Carbon remains as charcoal after heating sugar.

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Question (27)

QN002757

The droplets seen near the mouth of the boiling tube while heating sugar are formed from

(A) atmospheric dust
(B) water released from sugar
(C) sulfuric acid
(D) oxygen gas

Correct Answer: B

Explanation:

Heating sugar releases water vapour which condenses into droplets.

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Question (28)

QN002758

Sugar mainly contains the elements

(A) sodium, chlorine, oxygen
(B) carbon, hydrogen, oxygen
(C) iron, sulfur, oxygen
(D) copper, zinc, carbon

Correct Answer: B

Explanation:

Sugar is made of carbon, hydrogen, and oxygen.

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Question (29)

QN002759

A student heats a mixture of iron filings and sulfur powder. The black substance formed is

(A) iron oxide
(B) sulfur dioxide
(C) iron sulfide
(D) iron chloride

Correct Answer: C

Explanation:

Heating iron and sulfur forms iron sulfide.

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Question (30)

QN002760

Which sample gets attracted towards a magnet?

(A) Iron sulfide only
(B) Heated mixture only
(C) Iron and sulfur mixture
(D) Both samples equally

Correct Answer: C

Explanation:

Iron in the mixture is magnetic.

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Question (21)

A mobile phone contains many elements including aluminium, lithium, and cobalt. This shows that elements are

Explanation:

Link:

Question (22)

Which of the following cannot be separated by physical methods?

Explanation:

Link:

Question (23)

Sodium chloride is formed from sodium and chlorine in the ratio

Explanation:

Link:

Question (24)

Sodium chloride is commonly known as

Explanation:

Link:

Question (25)

Which observation proves that sugar is not an element?

Explanation:

Link:

Question (26)

On heating sugar strongly, the black residue left behind is mainly

Explanation:

Link:

Question (27)

The droplets seen near the mouth of the boiling tube while heating sugar are formed from

Explanation:

Link:

Question (28)

Sugar mainly contains the elements

Explanation:

Link:

Question (29)

A student heats a mixture of iron filings and sulfur powder. The black substance formed is

Explanation:

Link:

Question (30)

Which sample gets attracted towards a magnet?

Explanation:

Link:

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