You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
Litmus papers are indicators that differentiate between acidic, basic and neutral solutions. Red litmus changes to blue with basic solution If the colour of red litmus paper gets changed to blue, then it indicates that the given solution is a base and if there is no colour change, then it is either acidic or neutral. Whereas blue litmus turns to red with acidic solution. If the colour of blue litmus paper gets changed to red, then it indicates that the given solution is a acid and if there is no colour change, then it is either basic or neutral. This can be best explained by a simple experiment. Let's take 3 test tubes and labelled as A, B, and C which contain water, acidic and basic solutions respectively by using litmus paper test. We confirm that test tube A does not show any change in that indicates it is not acid and base. Test tube B also does not show any change in litmus paper. Only test tube C changes red litmus to blue indicating the solution is base.
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 do HCl, HNO3, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?
Why should curd and sour substances not be kept in brass and copper vessels?
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?
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.
What are the components of the transport system in highly organised plants?
What criteria do we use to decide whether something is alive?
What is the role of the acid in our stomach?
What could be the reasons for adopting contraceptive methods?
An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.
Which of the following correctly describes the magnetic field near a long straight wire?
(a) The field consists of straight lines perpendicular to the wire.
(b) The field consists of straight lines parallel to the wire.
(c) The field consists of radial lines originating from the wire.
(d) The field consists of concentric circles centred on the wire.
Can any source of energy be pollution-free? Why or why not?
List two methods of producing magnetic fields.
What is hydrogenation? What is its industrial application?
Can the wing of a butterfly and the wing of a bat be considered homologous organs? Why or why not?