Question

Q. 7 (a) A solution has a pH of 7. Explain how you would you :
(i) increase its pH
(ii) decrease its pH
(b) If a solution changes the colour of the litmus from red to blue, what can you say about its pH ?
(c) What can you say about the pH of a solution that liberates carbon dioxide from sodium carbonate ?
Q. 8 (a) Write two points of difference between electric energy and electric power. (6) Out of 60 W and 40 W lamps, which one has higher electrical resistance when in use

Answer 1

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7.(a) i)If you want to increase the pH of water, you must add an alkaline substance, such as baking powder, to it.

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ii)If you want to decrease the pH of water, you add an acidic substance, such as lemon juice.

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(b) If a solution had changed the color of litmus from red to blue than we can say that the solution is basic in nature.

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(c) The solution that liberates carbon dioxide from sodium carbonate has pH below 7 and hence acidic in nature.

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8.(a) Electrical energy defines the energy generated due to the movement of charge carriers in a conductor. While electrical power specifies the rate of consumption of electrical energy by a device. The SI unit of electrical energy is Joules. But electrical power is measured in Watts (or KWh).

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(b) Resistance and power are inversely proportional to each other. So, lamp powered 40 W has more resistance than a 60 W lamp.