The pH of three solutions is given in the table. Answer the questions that follow. Solution pH P 1 Q 7 R 14 Which of these solutions could possibly react with zinc metal to produce hydrogen gas?

Generally, a metal reacts with an acid to produce salt and hydrogen gas. When zinc metal reacts with strong acids like hydrochloric acid which has pH value nearly 1 , zinc chloride and hydrogen gas are formed. The reaction is shown below. Zn s + 2 HCl aq → ZnCl 2 aq + H 2 g Bases react with amphoteric metals to liberate hydrogen gas. Zinc reacts with strong base like sodium hydroxide (pH = 14 ) to form sodium zincate and hydrogen gas. The reaction is: Zn + 2 NaOH → Na 2 ZnO 2 + H 2 Hence, P and R solution which has pH 1 and 14 respectively can react with zinc.

Heating an alcohol with concentrated sulphuric acid results in the dehydration of the alcohol to give the alkene as shown by the reaction of ethanol to give ethene. CH 3 CH 2 OH → Hot conc . sulphuric acid CH 2 = CH 2 Pramila heated 2 -butanol (shown below) with concentrated sulphuric acid. Write the structural formulae of all the possible products of the reaction.

The reaction of 2 - butanol with concentrated sulfuric acid can lead to the formation of two possible products: 2 - butene and 1 - butene. The structural formulas of these products are as follows: 2 - butene: CH 3 CH = CHCH 3 1 - butene: CH 3 CH 2 CH = CH 2 In both cases, the sulfuric acid acts as a dehydrating agent, removing a water molecule from the alcohol to form the corresponding alkene.

The picture shows the bonds between atoms in two allotropes of carbon. Which allotrope is harder? Explain your answer.

The two allotropes of carbon are: Allotrope 1 - Graphite In the given structure of Graphite all the carbon atoms in are said to have stable chemical bonds with that of the other three carbon atoms, thus making the sheets. The carbon atoms in the Graphite structure are sp 2 hybridised and are directed in the same plane thus forming hexagonal rings. Due to this reason graphite is soft. Allotrope 2 - Diamond All the carbon atoms of Diamond make strong chemical bonds with that of the four other carbon atoms, thus making a perfect tetrahedron structure and on throughout the crystal. The carbon atoms, here are sp 3 hybridised, and the bond lengths of carbon-carbon atom are equal. Hence, Diamond forms a three-dimensional network of strong covalent bonds. Thus, it is the hardest substance. Hence, it can be concluded that Allotrope is harder than Allotrope 1.

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Science Textbook of Competency Based Questions for Class X>Chapter 4 - Acids, Bases and Salts>Exercise>Q 11

The pH of three solutions is given in the table. Answer the questions that follow.

Solution	pH
P	$1$
Q	$7$
R	$14$

Which of these solutions could possibly react with zinc metal to produce hydrogen gas?

MEDIUM

10th CBSE

IMPORTANT

Science Textbook of Competency Based Questions for Class X>Chapter 4 - Acids, Bases and Salts>Exercise>Q 14

A remarkable property of acids is that they can 'dissolve' metals. When metals are added to an acid, they disintegrate and disappear into the acid,

State one other common observation when metals 'dissolve' in acids, Explain the reason for this observation.

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10th CBSE

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Science Textbook of Competency Based Questions for Class X>Chapter 4 - Acids, Bases and Salts>Exercise>Q 15

A remarkable property of acids is that they can 'dissolve' metals. When metals are added to an acid, they disintegrate and disappear into the acid.

If the acid with the 'dissolved' metal is evaporated, can we get the metal back? Why or why not?

EASY

10th CBSE

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Science Textbook of Competency Based Questions for Class X>Chapter 4 - Acids, Bases and Salts>Exercise>Q 16

A remarkable property of acids is that they can 'dissolve' metals. When metals are added to an acid, they disintegrate and disappear into the acid.

In this question, the word 'dissolve' is used within quotes. This is because it is not actually an example of dissolving. What is the main difference between a metal 'dissolving' in an acid and sugar dissolving in water?

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10th CBSE

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Science Textbook of Competency Based Questions for Class X>Chapter 4 - Acids, Bases and Salts>Exercise>Q 34

Two salts X and Y are taken in two test tubes A and B, respectively and subjected to heating. Water is added to two test tubes, in case of A salt regains its original colour and in case of B water starts boiling. Then, X and Y may be, respectively:

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10th CBSE

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Science Textbook of Competency Based Questions for Class X>Chapter 4 - Acids, Bases and Salts>Exercise>Q 30

Heating an alcohol with concentrated sulphuric acid results in the dehydration of the alcohol to give the alkene as shown by the reaction of ethanol to give ethene.

${CH}_{3} {CH}_{2} OH \overset{Hot conc . sulphuric acid}{\to} {CH}_{2} = {CH}_{2}$

Pramila heated $2$ -butanol (shown below) with concentrated sulphuric acid.

Question Image

Write the structural formulae of all the possible products of the reaction.

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10th CBSE

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Science Textbook of Competency Based Questions for Class X>Chapter 4 - Carbon and its Compounds>Exercise>Q 9

The picture shows the bonds between atoms in two allotropes of carbon.

Question Image

Which allotrope is harder? Explain your answer.

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10th CBSE

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Science Textbook of Competency Based Questions for Class X>Chapter 4 - Acids, Bases and Salts>Exercise>Q 26

Dipti has three flasks containing dilute hydrochloric acid, dilute sulphuric acid and dilute sodium hydroxide respectively. The flasks are not labelled, and she does not have any pH indicator.
(a) Which of the solutions will she be able to identify just by making mixtures of pairs of the substances.
(b) What observation will help her to make this identification?

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