Chemical Reactions and Equations - Class 10 - Science
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Back Questions - Chemical Reactions and Equations | NCERT | Science | Class 10
Which of the statements about the reaction below are incorrect? $2 \mathrm{PbO}(\mathrm{s})+\mathrm{C}(\mathrm{s}) \rightarrow 2 \mathrm{~Pb}(\mathrm{~s})+\mathrm{CO}_{2}(\mathrm{~g})$
(a) Lead is getting reduced.
(b) Carbon dioxide is getting oxidised.
(c) Carbon is getting oxidised.
(d) Lead oxide is getting reduced.
(i) (a) and (b)
(ii) (a) and (c)
(iii) (a), (b) and (c)
(iv) all
Let's analyze each statement given the provided reaction:
$$ 2 \mathrm{PbO}(s) + \mathrm{C}(s) \rightarrow 2 \mathrm{Pb}(s) + \mathrm{CO}_2(g) $$
(a) Lead is getting reduced.
This is a correct statement. In the reaction, lead (Pb) is in a compound where it has an oxidation state of +2 (in ( \mathrm{PbO} )). It is transformed into elemental lead (( \mathrm{Pb} )) with an oxidation state of 0. Since the oxidation state of lead decreases, it is reduced.
(b) Carbon dioxide is getting oxidised.
This statement is incorrect. Carbon dioxide (( \mathrm{CO}_2 )) is a product of the reaction, and since it is not changing its oxidation state in the course of the given chemical equation, it is neither being oxidised nor reduced.
(c) Carbon is getting oxidised.
This is a correct statement. Carbon starts in the elemental form with an oxidation state of 0 and ends up in carbon dioxide (( \mathrm{CO}_2 )) with an oxidation state of +4. Since the oxidation state of carbon increases, it is being oxidised.
(d) Lead oxide is getting reduced.
This is a correct statement as it essentially restates (a) from the perspective of the compound ( \mathrm{PbO} ) rather than the element lead (Pb) itself.
Given the choices: (i) (a) and (b) - incorrect because (a) is true. (ii) (a) and (c) - incorrect because both (a) and (c) are true. (iii) (a), (b), and (c) - incorrect because (a) and (c) are true. (iv) all - incorrect because (a), (c), and (d) are true statements.
The only incorrect statement among (a), (b), (c), and (d) is (b), so there is no matching option in the given choices (i) to (iv). The question itself might be flawed because none of the options correctly identify the incorrect statement(s).
$\mathrm{Fe}_{2} \mathrm{O}_{3}+2 \mathrm{Al} \rightarrow \mathrm{Al}_{2} \mathrm{O}_{3}+2 \mathrm{Fe}$
The above reaction is an example of a
(a) combination reaction.
(b) double displacement reaction.
(c) decomposition reaction.
(d) displacement reaction.
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Sign up nowWhat happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer.
(a) Hydrogen gas and iron chloride are produced.
(b) Chlorine gas and iron hydroxide are produced.
(c) No reaction takes place.
(d) Iron salt and water are produced.
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Sign up nowWhat is a balanced chemical equation? Why should chemical equations be balanced?
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Sign up nowTranslate 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.
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Sign up nowBalance the following chemical equations.
(a) $\mathrm{HNO}_{3}+\mathrm{Ca}(\mathrm{OH})_{2} \rightarrow \mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}+\mathrm{H}_{2} \mathrm{O}$
(b) $\mathrm{NaOH}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}+\mathrm{H}_{2} \mathrm{O}$
(c) $\mathrm{NaCl}+\mathrm{AgNO}_{3} \rightarrow \mathrm{AgCl}+\mathrm{NaNO}_{3}$
(d) $\mathrm{BaCl}_{2}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{BaSO}_{4}+\mathrm{HCl}$
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Sign up nowWrite the balanced chemical equations for the following reactions.
(a) Calcium hydroxide + Carbon dioxide $\rightarrow$ Calcium carbonate + Water
(b) Zinc + Silver nitrate $\rightarrow$ Zinc nitrate + Silver
(c) Aluminium + Copper chloride $\rightarrow$ Aluminium chloride + Copper
(d) Barium chloride + Potassium sulphate $\rightarrow$ Barium sulphate + Potassium chloride
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Sign up nowWrite the balanced chemical equation for the following and identify the type of reaction in each case.
(a) Potassium bromide(aq) + Barium iodide(aq) $\rightarrow$ Potassium iodide(aq) + Barium bromide(s)
(b) Zinc carbonate(s) $\rightarrow$ Zinc oxide(s) + Carbon dioxide(g)
(c) Hydrogen(g) + Chlorine(g) $\rightarrow$ Hydrogen chloride(g)
(d) Magnesium(s) + Hydrochloric acid(aq) $\rightarrow$ Magnesium chloride(aq) + Hydrogen(g)
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Sign up nowWhat does one mean by exothermic and endothermic reactions? Give examples.
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Sign up nowWhy is respiration considered an exothermic reaction? Explain
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Sign up nowWhy are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
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Sign up nowWrite one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
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Sign up nowWhat is the difference between displacement and double displacement reactions? Write equations for these reactions.
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Sign up nowIn the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.
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Sign up nowWhat do you mean by a precipitation reaction? Explain by giving examples.
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Sign up nowExplain the following in terms of gain or loss of oxygen with two examples each.
(a) Oxidation
(b) Reduction
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Sign up nowA shiny brown coloured element ' $\mathrm{X}$ ' on heating in air becomes black in colour. Name the element ' $\mathrm{X}$ ' and the black coloured compound formed.
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Sign up nowWhy do we apply paint on iron articles?
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Sign up nowOil and fat containing food items are flushed with nitrogen. Why?
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Sign up nowExplain the following terms with one example each.
(a) Corrosion
(b) Rancidity
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Sign up nowExtra Questions - Chemical Reactions and Equations | NCERT | Science | Class 10
Which of the following elements is used to kill germs in water to make it safer?
A Oxygen
B Chlorine
C Nitrogen
D Hydrogen
The correct option is B: Chlorine.
Chlorine is added in small quantities to water to make it safer for consumption. It functions as an effective disinfectant because it is harmful to living organisms, allowing it to kill germs and other microorganisms present in the water. This property makes chlorine an essential element for water purification.
How to balance equations?
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Sign up nowThe sum total of all the reactions taking place in a cell is called reactions.
A. Anabolic
B. Catabolic
C. Amphibolic
D. Metabolic
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Sign up nowWhat is a displacement reaction?
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