Class 10 Science - Chapter Chemical reaction and Equation NCERT Solutions | Write the balanced chemical equations fo

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

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?

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?

Compare and contrast the arrangement of elements in Mendeléev’s Periodic Table and the Modern Periodic Table.

Will geographical isolation be a major factor in the speciation of a self-pollinating plant species? Why or why not?

We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. What should be the range of distance of the object from the mirror? What is the nature of the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this case.

Find out, from Table 10.3, the medium having highest optical density. Also find the medium with lowest optical density.

     Table 10.3 Absolute refractive index of some material media

Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?

What is the need for a system of control and coordination in an organism?

An example of homologous organs is

(a) our arm and a dog’s fore-leg.
(b) our teeth and an elephant’s tusks.
(c) potato and runners of grass.
(d) all of the above.

What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?

Explain the following.

(a) Why is the tungsten used almost exclusively for filament of electric lamps?
(b) Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal?
(c) Why is the series arrangement not used for domestic circuits?
(d) How does the resistance of a wire vary with its area of cross-section?
(e) Why are copper and aluminium wires usually employed for electricity transmission?

An electric oven of 2 kW power rating is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect? Explain.