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.
(a) Hydrogen gas combines with nitrogen to form ammonia
H2 + N2 ---------→ NH3
Hydrogen gas nitrogen gas Ammonia
3H2 + N2 -----------→ 3NH3
Hydrogen gas NItrogen gas Ammonia
(b) Hydrogen sulphide gas burns in air to give water and sulpur dioxide
H2S(g) + O2(g) ----------------→ H2O(l) + SO2(g)
Hydrogen sulphide gas Oxygen (from air) water Sulpur dioxide
2H2S(g) + 3O2(g) --------------→ 2H2O(l) + 2SO2(g)
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate
BaCl2(aq) + Al2(SO4)3(aq) --------→ AlCl3(aq) + BaSO4(s)
Barium chloride Aluminium sulphate Aluminium chloride Barium sulphate
3BaCl2(aq) + Al2(SO4)3(aq) -------→ 2AlCl3(aq) + 3BaSO4(s)
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas
K(s) + H2O(l) -----→ KOH(aq) + H2(g)
Potassium Water potassium hydroxide hydrogen gas
2K(s) + 2H2O(l) ------- → 2KOH(q) + H2(g)
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)
Explain the following terms with one example each.
(a) Corrosion
(b) Rancidity
Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
Explain the following in terms of gain or loss of oxygen with two examples each.
(a) Oxidation
(b) Reduction
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?
A shiny brown coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.
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?
Choose the correct option.
The magnetic field inside a long straight solenoid-carrying current
(a) is zero.
(b) decreases as we move towards its end.
(c) increases as we move towards its end.
(d) is the same at all points.
Will current flow more easily through a thick wire or a thin wire of the same material, when connected to the same source? Why?
You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be –
(a) 100 W (b) 75 W (c) 50 W (d) 25 W
Draw magnetic field lines around a bar magnet.
Samples of four metals A, B, C and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows.
Metal | Iron(II) sulphate | Cooper(II) sulphate | Zinc sulphate | Silver nitrate |
A | No reaction | Displacement | ||
B | Displacement | No reaction | Displacement | |
C | No reaction | No reaction | No reaction | No reaction |
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
What is the importance of DNA copying in reproduction?
Describe double circulation of blood in human beings. Why is it necessary?
What change will you observe if you test soap with litmus paper (red and blue)?