Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
Decompositive reaction in presence of Heat:
2Pb(NO3)2 (s) -- Heat → 2PbO (s) + 4NO2(g) + O2(g)
Lead Nitrate Leadoxide Nitrogen dioxide Oxygen
Decompositive reaction in presence of Light:
2AgCl - Light→ 2Ag + Cl2 gas
Silver Chloride (white) (grey)
Decompositive reaction by the use of electricity:
2H2O (l) -- Electricity→ 2H2 (g) + O2 (g)
water hydrogen gas oxygen gas
Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas.
Give an example of a double displacement reaction other than the one given in activity 1.10.
Why is respiration considered an exothermic reaction? Explain.
Identify the substances that are oxidised and the substance that are reduced in the following reactions.
(i) 4Na(s) + O2(g) → 2Na2O(s)
(ii) CuO(s) + H2(g) → Cu(s) + H2O(l)
Translate the following statements into chemical equations and then balance them.
(a) Hydrogen gas combines with nitrogen to form ammonia.
(b) Hydrogen sulphide gas burns in air to give water and sulpur dioxide.
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
Explain the following terms with one example each.
(a) Corrosion
(b) Rancidity
Explain the following in terms of gain or loss of oxygen with two examples each.
(a) Oxidation
(b) Reduction
Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
Write the balanced chemical equation for the following and identify the type of reaction in each case.
(a) Potassium bromide(aq) + Barium iodide(aq) → Potassium iodide(aq) + Barium bromide(s)
(b) Zinc carbonate(s) → Zinc oxide(s) + Carbon dioxide(g)
(c) Hydrogen(g) + Chlorine(g) → Hydrogen chloride(g)
(d) Magnesium(s) + Hydrochloric acid(aq) → Magnesium chloride(aq) + Hydrogen(g
What is a balanced chemical equation? Why should chemical equations be balanced?
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?
Define the principal focus of a concave mirror.
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?
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?
The refractive index of diamond is 2.42. What is the meaning of this statement?
A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?
Which of the following pairs will give displacement reactions?
(a) NaCl solution and copper metal
(b) MgCl2 solution and aluminium metal
(c) FeSO4 solution and silver metal
(d) AgNO3 solution and copper metal.
Which of the following groups contain only biodegradable items?
(a) Grass, flowers and leather
(b) Grass, wood and plastic
(c) Fruit-peels, cake and lime-juice
(d) Cake, wood and grass
You are given kerosene, turpentine and water. In which of these does the light travel fastest? Use the information given in Table 10.3.
Material medium |
Refractive index |
Material medium |
Refractive index |
Air | 1.0003 | Canada Balsam |
1.53 |
Ice | 1.31 | ||
Water | 1.33 | Rock salt | 1.54 |
Alcohol | 1.36 | ||
Kerosene | 1.44 | Carbon disulphide |
1.63 |
Fused quartz |
1.46 | ||
Turpentine oil |
1.47 | Ruby | 1.71 |
Benzene | 1.50 | Sapphire | 1.77 |
Crown glass |
1.52 | Diamond | 2.42 |
What are the different ways in which individuals with a particular trait may increase in a population?
Explain the mechanism of the cleaning action of soaps.
The anther contains
(a) sepals.
(b) ovules.
(c) pistil.
(d) pollen grains.
Two circular coils A and B are placed closed to each other. If the current in the coil A is changed, will some current be induced in the coil B? Give reason.