Class 10 Chemistry Chapter 1 Important Question | Chemical Reaction and Equation

 Chapter - 1 - Chemical Reaction and Equation.




Most Important Questions :- 


Q1. Which of the following gases is used to store fat and oil-containing foods for a long time?
a)Carbon dioxide
b)Oxygen
c)Nitrogen
d) Neon


Answer:


(c) Nitrogen gas is used to store fat and oil-containing foods for a long time.



Q2. Which of following used in Black and White Photography -
a) Lead Nitrate 
b) Magnesium Oxide 
c) Silver Bromide 
d) Silver Nitrate

Answer :-


 (C) Silver Bromide 




Q3. The element 'X' burn with white dazzling flame in the presence of air and used in biochemical reactions .
Identify the element and write the chemical equation. 

Answer :-

The element 'X' is Magnesium 

Chemical equation - 
                                          2Mg + O2 → 2MgO


Q 3 . What is Rancidity and why we fill nitrogen in chips packets ? 

Answer : 

When oil or fat containing foods get oxidised they change their taste and become rancid and the phenomenon is called Rancidity.

We fill nitrogen in chips packets to save them from getting rancid . Chips contain fat , therefore, they can become rancid when react with oxygen , therefore, to avoid them from getting rancid we fill nitrogen which is a anti oxidant agent .


Q4. What is Corrosion ? 

Answer - 

The attack of acid , mositure etc. on metals is called Corrosion.


Q5. What is Chemical Reactions? 
Answer :- 

When one or more substance undergoes chemical change to produce one or more new substances , it is called Chemical Reactions.



Q6. Identify the reducing agent in the following reactions

(a ) 4 NH3 + 5 O2 → 4 NO + 6 H2O

(b ) H2O + F2 → HF + HOF

(c ) Fe2O3 + 3 CO → 2 Fe + 3 CO2

(d ) 2 H2 + O2 → 2 H2O

Answer:

(a ) Here, ammonia (NH3 ) is the reducing agent.

(b ) Here, water (H2O) is the reducing agent.

(c ) Here, carbon monoxide (CO) is the reducing agent.

(d ) Here, hydrogen (H2 ) is the reducing agent.



Q7. Grapes hanging on the plant do not ferment, but after being plucked from the plant can be fermented. Under what conditions do these grapes ferment? Is it a chemical or a physical change?

Answer:

When attached to the plants, Grapes are living, and therefore, their immune system prevents fermentation. The microbes can grow in the plucked grapes, which can be fermented under anaerobic conditions. This is a chemical change.



Q8. A substance X, an oxide of a group 2 element, is used intensively in the cement industry. This element is present in bones also. On treatment with water, it forms a solution which turns red litmus blue. Identify X and also write the chemical reactions involved.

Answer:

Here, X is calcium oxide.

Calcium oxide is used intensively in the cement industry.
The element present in it (in bones also) is calcium.
On treatment with water, calcium oxide forms a solution of calcium hydroxide [Ca(OH)2], which is an alkali. Hence, it turns red litmus blue.
CaO (s) + H2O (l) → Ca(OH)2 (aq) + Heat

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