Class 10 Chemical Reaction And Equations Important Questions

Q.1.

A water insoluble substance ‘X’ on reacting with dilute H₂SO₄ released a colourless and odourless gas accompanied by brisk effervescence. When the gas was passed through water, the solution obtained turned blue litmus red. On bubbling the gas through lime water, it initially became milky and milkyness disappeared when the gas was passed in excess. Identify the substance ‘X’. Write its chemical equations of the reactions involved.

Ans.

The water insoluble substance ‘X’ is metal carbonate CaCO₃.

CaCO_{3 (S)} + H₂SO_{4 (Aq)}  CaSO_4(Aq) + H₂O _(Aq) + CO_{2 (G)}

Ca(OH)₂ + CO_{2 (G)}CaCO_{3 (S)} + H₂O _(L)

(milky)

CaCO_{3 (S)} + CO_{2 (G)}+ H₂O _(Aq)CaHCO₃

(milkiness disappeared)

Q.2.

Ahmad took a magnesium ribbon (cleaned) and burned it on a flame. The white powder formed was taken in a test tube and water was added to it. He then tested the solution formed with red and blue litmus paper. What change was seen? Why?

Ans.

Red litmus paper turned blue.

Blue litmus paper remained blue.

This is because the magnesium ribbon on burning in air forms the white magnesium oxide. Which dissolved in water, it forms magnesium hydroxide, which is Basic in nature.

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Q.3.

Give one example of a combination reaction in which an element combines with a compound to give you a new compound.

Ans.

O₂ + 2SO₂ 2SO₃

8NH₃ + 3Cl₂ 6NH₄Cl +N₂

Q.4.

Marble statues often slowly get corroded when kept in open for a long time. Assign a suitable explanation.

Q.5.

Mohan took pure water for the electrolytic decomposition of water but did not see any bubbles near the electrodes. Explain why?

Q. 6

Rancidity is a process used for spoiling of cooked food materials like vegetables, etc. When kept for long time in open. How can you prevent such process to proceed? Give an example.

Q. 7

A substance ‘X’ displaces ‘Y’ from its solution in water. It is called displacement reaction. What other chemical name can be given to such type of reactions? Explain, giving an example?

Q. 8

A grey coloured metal ‘Z’ (Atomic weight=65) is used in making dry cell. It reacts with dil. HCl to liberate a gas. What is the gas evolved? Calculate the minimum amount of ‘Z’ required to produce 100 litre of gas?

Q. 9

Why respiration is considered an exothermic reaction? Explain.

Q. 10

Why photosynthesis is considered an endothermic reaction? Explain.

Q. 11

Why decomposition reactions are called opposite of combination reactions? Write equations for these reactions.

Q. 12

A shiny brown coloured element ‘X’ on heating in air becomes a black coloured compound. Name the element ‘X’& black the coloured compound formed. Also write the equation

Oral questions (Conversation type)

ORAL QUESTIONS

What is opposite to combination reaction?

To pack food articles, why do manufacturers flush out oxygen with nitrogen?

What is spoiling of food called, when kept for a long time?

What is the chemical reaction called, in which heat is evolved?

Silver articles get black coating. Name the phenomenon.

Which gas is evolved when acid is added to lime stone?

When a more reactive metal displaces a less reactive metal in solution, what is the reaction called?

What sign (+ or -) is given to exothermic reaction?

Which of the two is a redox reaction?

What is one important similarity between rusting and burning?

QUIZ - WHO AM I

I am symbolic representation of a chemical change.

I am a metal which go on losing weight when constantly exposed to air and moisture.

I conduct electric current and get a green coating when exposed to humid atmosphere for long.

My blue colour starts fading when zinc metal is added to my aqueous solution.

I get reduced in a redox reaction.

I am formed during a chemical change.

I separate reactants from products when a chemical reaction is represented by a chemical equation.

I give a name to the reaction between acids and bases.

I am a chemical reaction which represents digestion of food in our body/

I am a process which is used to prevent rusting of iron objects / articles.