Give scientific reasons.
a.When the gas formed on heating limstone is passed through freshly prepared lime water, the lime water turns milky.
b. It takes time for pieces of Shahabad tile to disappear in HCl, but its powder disappears rapidly.
c.While preparing dilute sulphuric acid from concentrated sulphuric acid in the laboratory, the concentrated sulphuric acid is added slowly to water with constant stirring.
d. It is reccommended to use air tight container for storing oil for long time.

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Solution

Give scientific reasons.

a.
Limestone is made up of calcium carbonate.When calcium carbonate is heated Carbon dioxide is evolved. Lime water is made up of Calcium hydroxide.
When carbon dioxide is passed through lime water, the Carbon dioxide reacts with calcium hydroxide to form Calcium carbonate which is a white precipitate, then lime water turns milky as there is formation of calcium carbonate.
$C a C o_{3} \to C a O + C O_{2} C O_{2} + C a (O H)_{2} \to C a C O_{3}$

b. It takes time for pieces of Shahabad tile to disappear in HCl, but its powder disappears rapidly because in pieces of the tile, the surface atoms can only react with HCl but in powdered form all the atoms can react with HCl. This makes the difference in their reactivity. Powders are simpler substances of the pieces and they take lesser time for the reaction as compare to whole piece of tile, which is a compound.
for example: powdered salt react and water will dissolve, but salt rocks and water will not dissolve.

c.While preparing dilute sulphuric acid from concentrated sulphuric acid in the laboratory, the concentrated sulphuric acid is added slowly to water with constant stirring because sulphuric acid (H₂SO₄) reacts very vigorously with water, it is a highly exothermic reaction. If you add water to concentrated sulphuric acid, it can boil and bump out due to which you may get a nasty acid burn.Water is a good absorber of heat, so we add acid to the water, slowly and with constant stirring.

d. It is recommended to use air tight container for storing oil for long time in order to avoid the problem of rancidity. Rancidity is the condition produced by aerial oxidation of fats and oils marked by unpleasant smell and taste.

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Similar questions

Q. While preparing dilute sulphuric acid from concentrated sulphuric acid in the laboratory, the concentrated sulphuric acid is added slowly to water with constant stirring. Explain why ?

Give reasons for the following:
(i) In the contact process, sulphur trioxide formed is dissolved in 98% sulphuric acid and not in water.
(ii) When solution of sulphur dioxide is exposed to air, it gets converted to sulphuric acid.
(iii) When diluting concentrated sulphuric acid, the acid should be added to water and not water to the acid.
(iv) When concentrated sulphuric acid is exposed to air, its volume increases and it becomes slightly dilute.
(v) Sulphuric acid can form two kinds of salts with sodium chloride.
(vi) When barium chloride is added to dilute sulphuric acid, a white precipitate is formed.
(vii) When carbon is heated with concentrated sulphuric acid, carbon dioxide is formed.
(viii) Ammonia gas cannot be dried by passing through concentrated sulphuric acid.
(ix) When concentrated sulphuric acid is added to sugar/glucose, a black mass is left behind.
(x) Concentrated sulphuric acid should not be added to oxalic acid or formic acid in the open laboratory.
(xi) When concentrated sulphuric acid is added to blue crystalline copper sulphate, it turns powdery white.
(xii) Concentrated sulphuric acid must be stored in airtight bottles.
(xiii) Cotton clothes get burnt with concentrated sulphuric acid.
(xiv) H₂SO₄ cannot be prepared by heating sodium sulphate with conc. HCl or HNO₃.

Suppose, in your lab, you have run out of dilute Sulphuric acid. You require dilute $H_{2} S O_{4}$ for an important synthesis but only have concentrated Sulphuric acid, water and a glass beaker. How will you synthesize dilute $H_{2} S O_{4}$ ?

Q. Give reasons:
When the gas formed on heating limstone is passed through freshly prepared lime water, the lime water turns milky.

Q. What happens when (given balanced equation):
(a) Sulphur is added to hot and conc. HNO₃?
(b) Nitric acid is added to KI (aq)?
(c) Nitric acid is dissolved in large amount of water?
(d) Nitric acid is added to washing soda and the resulting gas is passed through a freshly prepared lime water?
(e) Limestone reacts with nitric acid?

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