What effect does the concentration of H+(aq) ions have on the nature of the solution?
Concentration of H+ can have a varied effect on the nature of the solution. H+ ion concentration increases, the solution becomes more acidic, while a decrease of H+ ion causes an increase in the basicity of the solution.
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
Give two important uses of washing soda and baking soda.
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?
Name the substance which on treatment with chlorine yields bleaching powder.
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.
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?
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.
The autotrophic mode of nutrition requires
(a) carbon dioxide and water. (c) sunlight.
(b) chlorophyll. (d) all of the above.
Besides gallium, which other elements have since been discovered that were left by Mendeléev in his Periodic Table? (any two)
How do Mendel’s experiments show that traits may be dominant or recessive?
Draw the structure for the following compounds.
(i) Ethanoic acid (ii) Bromopentane*
(iii) Butanone (iv) Hexanal.
*Are structural isomers possible for bromopentane?
What are alloys?
The kidneys in human beings are a part of the system for
(a) nutrition. (c) excretion.
(b) respiration. (d) transportation.
A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is
(a) towards south (b) towards east
(c) downward (d) upward
What is the role of decomposers in the ecosystem?
What does an electric circuit mean?
Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).