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प्रश्न
What is a chemical reaction?
उत्तर
“Chemical reaction is a chemical change in which matter changes into a new substance or substances.”
APPEARS IN
संबंधित प्रश्न
Changes in which new substances are formed are called ______ changes.
Give one example that illustrates the following characteristics of a chemical reaction:
Change in state
Complete and balance the following chemical equations:
\[\ce{Pb(NO3)2->[heat]}\] _________
MULTIPLE CHOICE QUESTIONS
Tick the most appropriate answer.
Compounds, which in their molten state allow an electric current to pass through them are called
- electrolytes
- non-electrolytes
- non-conductors
- none of these
TRUE \ FALSE
Evaporation of water is a physical change. True or false ?
What are the characteristics of a chemical reaction ? A chemical reaction is characterised by an irreversible change in which a new substance is formed.
Write true or false :
Hydrogen sulphide has rotten egg smell .
Balance the following equation :
Fe + H2O → Fe3O4 + H2
Name the type of chemical reaction shown by the following equation :
Fe2O3 + 2Al → Al2O3 + 2Fe
Out of sodium and sulphur which is a metal? Explain its reaction with the oxygen.
State the type of reactions for the following represent and balance the ones that are not balanced.
Cl2 + 2KBr → 2KCl + Br2
What do you understand by 'chemical reaction'?
State the original colour of the following substance and colour of residue obtained after heating.
Ammonium dichromate
Give a chemical test to distinguish between the following gases.
NH3 and HCl
Give a word equation for the following reaction.
Two gases which combine to give a solid.
Give reason for the following:
The catalytic oxidation of sulphur dioxide to sulphur trioxide is represented by a double arrow {⇌}
between the reactants and products, formed in the chemical reaction.
Give two examples where a chemical reaction is accompanied by a change in colour of the reactants and products on completion of the reaction.
What happens when cane sugar is strongly heated? Mention any two changes in it.
Mention the various conditions required for a chemical reaction to occur.
Discuss how acid rain occurs due to emission of smoke from vehicles and industries?
When lithium metal is placed in hydrochloric acid, _______ gas is evolved.
Anaerobic bacteria digest animal waste and produce biogas (Change – A). The biogas is then burnt as fuel (Change – B). The following statements pertain to these changes. Choose the correct one.
Chemical change is a temporary change.
Two chemical species X and Y combine together to form a product P which contains both X and Y
\[\ce{X + Y -> P}\]
X and Y cannot be broken down into simpler substances by simple chemical reactions. Which of the following concerning the species X, Y and P are correct?
(i) P is a compound
(ii) X and Y are compounds
(iii) X and Y are elements
(iv) P has a fixed composition
Classify each of the following, as a physical or a chemical change. Give reasons.
(a) Drying of a shirt in the sun.
(b) Rising of hot air over a radiator.
(c) Burning of kerosene in a lantern.
(d) Change the colour of black tea by adding lemon juice to it.
(e) Churning of milk cream to get butter.
A chemical change may involve –
Which of the following statement is incorrect for a chemical reaction?
Iron and rust are the same substances.
The chemical name of baking soda is sodium bicarbonate.
Is the conversion of milk into ice cream a chemical change?
