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प्रश्न
State four conditions necessary for a chemical reaction to take place.
उत्तर
Ans: Close contact— For a chemical reaction to take place the reactants should be brought in close contact i.e., they should be mixed,
\[\ce{Sodium + Water -> Sodium hydroxide + Water}\]
Solution form— Some substances react with each other only when they are mixed in the solution form, e.g.,
\[\ce{\underset{\text{(aq.)}}{Silver nitrate} + \underset{\text{(aq.)}}{Sodium chloride} ->\underset{\text{(ppt.)}}{Silver nitrate}+\underset{\text{(aq.)}}{Sodium nitrate}}\]
Heat— Some reactants need to be heated to undergo a chemical change, e.g.,
\[\ce{Potassium chlorate->[heat] Potassium chloride + oxygen}\]
Light— Some reactions take place in the presence of light.
\[\ce{Carbon dioxide + Water ->[chlrophyll][sunlight] Glucose + Oxygen}\]
APPEARS IN
संबंधित प्रश्न
How do the following help in bringing about a chemical change?
heat.
What are (i) positive catalysts and (ii) negative catalysts? Support your answer with one example for each of them.
Complete and balance the following chemical equations:
Ba`"CI"_2` + `"H"_2"SO"_4` `→`
(aq.) (aq.)
Write the missing reactants and products and balance the equations.
................+ HCI `→` NaCI + `"H"_2"O"` + .........................
MULTIPLE CHOICE QUESTIONS
Tick the most appropriate answer
Which of the following is a reducing agent?
- oxygen
- chlorine
- hydrogen
- none of these
FILL IN THE BLANK
In a double decomposition precipitation reaction both the reactants must be ............ soluble.
TRUE \ FALSE
Weak electrolytes dissociate partially in their aqueous or fused state.
Fill in the blank
A new substance is always formed in a _______ change.
Fill in the blank
A change in which the substance can be brought back to its original state is called a _______ change.
A solution of a substance ‘X’ is used for white washing write the reaction of the substance ‘X’ named in (a) above with water.
Choose the correct option from the bracket and explain the statement giving reason.
(Oxidation, displacement, electrolysis, reduction, zinc, copper, double displacement, decomposition)
To prevent rusting, a layer of ______ metal is applied on iron sheets.
Complete the statement by filling the gaps using appropriate term from the terms given in the bracket.
(slow, coloured, arrow, fast, smell, milky, physical, product, chemical, reactant, covalent, ionic, octet, duplet, exchange, sharing, equality sign)
An ______ is drawn in between the reactants and products while writing the equation for a chemical reaction.
Give reason for the following:
Molybdenum is used in the manufacture of ammonia.
Multiple choice:
Which of the following is not a characteristic of a chemical change?
Give a chemical test to distinguish between the following gases.
H2 and O2
What do you observe when dilute sulphuric acid is added to the following:
Sodium Sulphide
Write your observation and a balanced equation in the case of the following substances being heated.
Copper nitrate.
Explain the term ‘chemical reaction’ with special reference to – ‘reactants’ and ‘products’.
Select the correct answer for the following options:
The pale blue precipitated obtained when copper [II] sulphate reacts with sodium hydroxide.
State the following reaction represent oxidation or reduction.
\[\ce{Cu++->Cu}\]
Give two examples where a chemical reaction is accompanied by a change in colour of the reactants and products on completion of the reaction.
Give a balanced equation for the conversion of an ammonium salt to a basic gas.
______ is not a chemical change.
What is the role of a catalyst in a chemical reaction?
What is the use of indicator?
The chemical name of baking soda is sodium bicarbonate.
Which is used as a catalyst during the process of hydrogenation of oils?
Give an example where heat, light, and sound are produced during a chemical change.
What is thermochemical reactions?
Write the effects of chemical reactions.
