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प्रश्न
Give the characteristic tests for the following gases :
- CO2
- SO2
- O2
- H2
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उत्तर
- CO2 gas : It is a colourless and odourless gas. When passed through lime water, it will initially become milky.
`underset("Lime water")("Ca"("OH")_2("aq")) + "CO"_2("g") -> "CaCO"_3("s") + "H"_2"O"("aq")`
The milkiness will disappear on passing the gas in excess.
`"CaCO"_3("s") + "CO"_2("g") + "H"_2"O" ("aq") -> underset("Colourless")("Ca"("HCO"_3)_2("aq"))` - SO2 gas : It is a colourless but a pungent smelling gas. The gas when passed through an acidified solution of potassium permanganate (pink) will decolourise it.
`underset("(Orange)")("K"_2"Cr"_2"O"_7) + 3"SO"_2 + "H"_2"SO"_4 -> "K"_2"SO"_4 + underset("(Light green)")("Cr"_2("SO"_4)_3) + "H"_2"O"` - Oxygen gas : The gas is a supporter of combustion. It can be tested by bringing a burning or smouldering match-stick near the mouth of the test tube from which the gas escapes. The match-stick will burn more brightly.
- Hydrogen gas : The gas itself is combustible. It will burn with a pop sound when a burning candle or match- stick is brought near it.
`2"H"_2("g") + "O"_2("g") -> 2"H"_2"O"("g")`
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संबंधित प्रश्न
Give one example of a chemical reaction.
Balance the given equation:
BaCI2 + H2SO4 
BaSO4 + HCI
Give one example of a chemical reaction characterised by formation of a precipitate.
What do you understand by exothermic reactions?
The chemical reaction between two substances is characterised by a change in colour from orange to green. These two substances are most likely to be:
(a) potassium dichromate solution and sulphur dioxide
(b) potassium permanganate solution and sulphur dioxide
(c) potassium permanganate solution and lemon juice
(d) potassium dichromate solution and carbon dioxide.
Which of the following is not an endothermic reaction?
(a) CaCO3 → CaO + CO2
(b) 2H2O →2H2 + O2
(c) 6CO2 + 6H2O → C6H12O6 + 6O2
(d) C6H12O6 + 6O2 → 6CO2 + 6H2O
One of the following is an exothermic reaction. This is:
(a) electrolysis of water
(b) conversion of limestone into quicklime
(c) process of respiration
(d) process of photosynthesis
Write word equation for the following skeletal equation:
\[\ce{NaOH + H2SO4 -> Na2SO4 + H2O}\]
Balance the following chemical equation :
FeS + HCl → FeCl2 + H2S
Balance the following chemical equation :
H2 + O2 → H2O
Write your observation for the following chemical reaction and name the product formed :
When dilute acetic acid is poured on baking soda.
Write symbolic representation for the following word equation and balance them :
Aluminium + Chlorine → Aluminium chloride.
Write your observation and name the product when ron nails are added to an aqueous solution of copper sulphate.
Balance the equation stepwise.
SO2(g) + H2S(aq) → S(s) + H2O(l)
Balance the following equation:
Fe + H2O → Fe3O4 + H2
Match column A with column B.
| Column A | Column B |
| (a) Blue salt changes to white and then black | (i) Ammonium dichromate |
| (b) Orange coloured compound changes to green. | (ii) Iodine |
| (c) Red compound changes to brown and then yellow. | (iii) Zinc Nitrate |
| (d) White to yellow when hot and white when cold. | (iv) Copper sulphate |
| (e) Violet solid changes to violet vapours. | (v) Red Lead |
Define: Endothermic reaction
Answer the following question:
How do acids and bases react with each other? What is the name of the process? What product is obtained from these reactions?
Underline the compound in the equation given below, it is incorrectly balanced and write the correct balancing for the same.
Na2SO3 + HCl → 2NaCl + H2O + SO2
Balance the given chemical reaction as per the instructions below.
\[\ce{NaOH + H2SO4 -> Na2SO4 + H2O}\]
Write names of reactants and products of chemical reaction.
