CBSE 10th Standard Science Subject Chemical Reactions and Equations HOT Questions 2 Mark Questions With Solution 2021
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CBSE 10th Standard Science Subject Chemical Reactions and Equations HOT Questions 2 Mark Questions With Solution 2021
10th Standard CBSE
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Reg.No. :
Science
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A yellowish coloured compound 'A' is photosensitive material. On exposure to sunlight, it gives a greyish substance 'B' and brown fumes of a gas 'C'. Identify A, B and C. How will you obtain A from the nitrate salt of B?
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A substance 'A' displaces 'B' from its solution in water. It is called displacement reaction. What other chemical name can be given to such type of reactions? Explain with an example.
(a) -
In the reaction:
2KClO3 \(\overset { \Delta/MnO_2 }{ \rightarrow } \) 2KCl + 3O2, what does the '\(\Delta\)' and 'MnO2' signify? What type of reaction is this?(a) -
A metal X available in the form of ribbon burns in air with a dazzling white light once heated to its ignition temperature. It leaves a white powder Y which dissolves in water. The solution so formed turns red litmus blue. Identify X and Y and write a balanced chemical equation of the reaction.
(a) Identify 'X' and 'Y'.
(b) Write a balanced chemical equation for this reaction.(a) -
A pinch of solid sodium carbonate is added into dilute hydrochloric acid in a test tube. Sodium chloride and water formed remains the solution whereas the carbon dioxide escapes out. The tube found to become hot.
(a) Represent it in word equation.
(b) Give the formula of the word equation.
(c) Balance the equation.
(d) How will the reaction be represented to make it maximum informative?(a)
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CBSE 10th Standard Science Subject Chemical Reactions and Equations HOT Questions 2 Mark Questions With Solution 2021 Answer Keys
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The yellowish compound is silver bromide [AgBr].
When silver bromide is exposed to sun light, it produces a grey coloured silver metal.
\(2AgBr\longrightarrow2Ag+Br_2\)
Thus 'A' is silver bromide [AgBr], 'B' is silver metal [Ag] and 'C' is bromine [Br2]
The nitrate of 'B' is silver nitrate [AgNO3]
Silver nitrate when treated with sodium bromide, it forms silver bromide.
AgNO3+NaBr\(\rightarrow\)AgBr+NaNO3 -
A substance 'A' which displaces 'B' from its solution in water must be higher in reactivity. Therefore, 'A' must be high reactivity metal, let us say zinc(Zn). The 'B' must be copper sulphate solution. This is because copper is least reactive than zinc.
CuSO4+Zn\(\rightarrow\)ZnSO4+Cu
In this reaction, zinc is oxidised to zinc sulphate and copper sulphate is reduced to copper metal. Thus this reaction is also called redox reaction. -
The above reaction is a decomposition reaction. The symbol \(\Delta\) represents the heat and the MnO2 represents that it acts as a catalyst for the decomposition reaction to take place. Since the decomposition takes place in presence of heat, the reaction is thermal decomposition.
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(a) When magnesium is heated in oxygen of air, it leaves white powder of magnesium oxide which dissolves in water. The magnesium oxide being alkaline in nature turns red litmus to blue. Also, the metal in ribbon form is Magnesium [Mg]. Thus 'X' is identified ad magnesium and 'Y' is identified as magnesium oxide.
(b)The chemical reaction is:
2Mg(s)+O2(g)\(\rightarrow\)2MgO -
(a) Represent the statement in word equation
Sodium carbonate + Hydrochloride acid \(\rightarrow\) Sodium chloride + Water Carbon dioxide
(b) Give the formula to the word equation Na2CO3+HCl\(\rightarrow\)NaCl+H2O+CO2
(c) Balance the equation.
Na2CO3 + 2HCl \(\rightarrow\) 2NaCl + H2O + CO2
(d) Write the physical states
Na2CO3(s)+2HCl(aq)\(\rightarrow\) 2NaCl(s)+H2O(l)+CO2(g)
