Give two important uses of washing soda and baking soda.
Two important uses of washing soda and baking soda are:
1) Washing soda:
(a) Washing soda is used to remove permanent hardness of water.
(b) It is used for domestic household washing purposes.
(c) It is used in glass, soap, and paper industries.
2) Baking soda:
(a) Baking powder is prepared by using baking soda. Baking powder is formed by the mixture of baking soda with a mild acid known as tartaric acid. When it is heated or mixed in water, CO2 gas is evolved that makes bread or cake fluffy.
(b) Soda-acid fire extinguishers are prepared by baking soda.
(c) It is used in making pakora more crispy.
Why does distilled water not conduct electricity, whereas rain water does?
Plaster of Paris should be stored in a moisture-proof container. Explain why?
A solution turns red litmus blue, its pH is likely to be
(a) 1 (b) 4 (c) 5 (d) 10
Why should curd and sour substances not be kept in brass and copper vessels?
Why do HCl, HNO3, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?
Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test for the presence of this gas?
Five solutions A,B,C,D and E when tested with universal indicator showed pH as 4,1,11,7 and 9, respectively. Which solution is
(a) neutral?
(b) strongly alkaline?
(c) strongly acidic?
(d) weakly acidic?
(e) weakly alkaline?
Arrange the pH in increasing order of hydrogen-ion concentration.
Name the substance which on treatment with chlorine yields bleaching powder.
A milkman adds a very small amount of baking soda to fresh milk.
(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
(b) Why does this milk take a long time to set as curd?
Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
What is a good source of energy?
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
What changes can you make in your habits to become more environment-friendly?
What is the difference between a reflex action and walking?
What is the importance of DNA copying in reproduction?
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Why should a magnesium ribbon be cleared before burning in air?
Define the principal focus of a concave mirror.
Describe double circulation of blood in human beings. Why is it necessary?
Write equations for the reactions of
(i) iron with steam
(ii) calcium and potassium with water.
What kind of mirror – concave, convex or plain – would be best suited for use in a solar cooker? Why?
Why do ionic compounds have high melting points?
How are water and minerals transported in plants?
How does our body respond when adrenaline is secreted into the blood?
One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.
What changes would you suggest in your home in order to be environment-friendly?
What are plant hormones?
What are the different ways in which individuals with a particular trait may increase in a population?