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प्रश्न
Give examples of exothermic reactions i.e. heat evolved in each of the following:
(a) reaction between a solid and a liquid
(b) reaction between two gases
Give two examples of exothermic reactions seen in everyday life.
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उत्तर
(a) Reaction between a solid and a liquid:
CaO + H2O → Ca(OH)3 + Δ
(b) Reaction between two gases are:
\[\ce{N2 + 3H2 ⇌[Fe-450°][200 atoms.] 2NH3 + \triangle}\]
[finely divided iron (Fe) - catalyst]
Examples of exothermic reactions are:
- Rusting of iron – the reaction is slow and the heat evolved is very less, hence unnoticeable.
- Setting of cement – cement setting liberates heat, hence concrete structures are set slowly.
- Human Body – many chemical reactions in our body are exothermic & provide energy to survive.
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संबंधित प्रश्न
State whether the following statement is true or false. In case a statement is false, write the corrected statement.
Iron pipes coated with zinc do not get rusted easily.
Changes in which new substances are formed are called ______ changes.
TRUE \ FALSE
Weak electrolytes dissociate partially in their aqueous or fused state.
How is precipitate formation in a chemical reaction indicated?
Write a short note on the information derived from a balanced chemical equation.
True or false
New substances are formed in a chemical change.
Write true or false :
When iron and sulphur are heated together a grey mass is formed which is attracted by a magnet .
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)
A colourless solution of calcium hydroxide in a test tube turns ______ on blowing in it through a blow tube for some time.
Show with the help of diagram of electronic configuration how the following compound is formed from the constituent atoms.
Sodium chloride
State the type of reactions for the following represent and balance the ones that are not balanced.
Cl2 + 2KBr → 2KCl + Br2
Name: A brown gas
Give a chemical test to distinguish between the following gases.
H2 and CO2
Write your observation and a balanced equation in the case of the following substances being heated.
Ammonium dichromate.
On heating which of the following substances i.e. copper carbonate, zinc carbonate, washing soda, copper sulphate, zinc nitrate, copper nitrate, lead nitrate, ammonium chloride and ammonium dichromate – relate to the reaction given below.
A coloured substance which leaves on strong heating a black residue and evolves two colourless gases one of which is acidic and the other neutral.
Select the correct answer from the options given below:
State the gaseous product formed, when
An active metal reacts with dilute sulphuric acid.
Rusting of Iron: undesirable change:: Dead plants turn into manure: ______.
Match the following:
| 1. | Sodium Chloride | a. | CaSO41/2H2O |
| 2. | Calcium sulphate dihydrate | b. | C2H5Oh |
| 3. | Magnesium sulphate hydrate | c. | CaSO4.2H2O |
| 4. | Calcium sulphate hemihydrate | d. | NaCl |
| 5. | Phenol | e. | MgSO4.H2O |
Which of the following is a chemical change?
State whether the following statement is true or false:
When a candle burns, both physical and chemical changes take place.
Define the following term:
Chemical change
