Question 1
Give reason:-
(I) How is the concentration of hydronium ions(H³0+) affected when a solution of an acid is diluted?
Answer:-
Concentration of hydronium ions is decreased when the solution of an acid is diluted.
(II) Why should an aqueous solution of an acid conduct electricity?
Answer:-Electricity conducted in a solution by the ions. An acid release , H+ ions or hydronium in solution, therefore it conduct electricity.
(III) Why does dry HCL do not change the colour of dry litmus paper?
Answer:-
Colour of litmus paper will change only when it comes into contact with H+ ions. Hydrogen ions produce when HCL gas comes into contact with water. Therefore dry HCL do not change their colour of litmus paper.
(IV) Why do acid show acidic behaviour in absence of water?
Answer:-
Acid produce H+ ions or hydronium ions are not produce in absence of water.
HCL+H20-------> H³0+Cl
Question 2
What is observed when calcium oxide reacts with water taken in a beaker? Write equation for the chemical reaction and name the type of reaction in the case.
Answer:-
Question 3
What is observed when ferrous sulphate is heated in a test-tube. Write the equation involved in this chemical reaction and also write the name of type of reaction.
Answer:-
Question 4
A student added iron metal in two test tubes 'A and B' containing aqueous solution of aluminium sulphate and copper sulphate. And which test tube the student will observe colours change? On the basis of this experiment , state which metal (aluminium,copper or iron) is most reactive metal?
Answer:-
Question 5
A student has taken sodium hydroxide solution in a test tube and poured red and blue litmus paper strips into it respectively. The student would observe a change in colour in which strip of litmus paper and why?
Answer:-
Question 6
Under what soil conditions do you think a farmer would treat the soil of his field with quick line or slaked lime or chalk? Explain.
Answer:-
Quicklime, slaked lime and chalk are basic in nature. When they react with acids, neutralization reaction takes place. If the soil is too acidic and not good for cultivation, then to neutralize the acidity of soil, the farmer would treat the soil with these substances.
Question 7
Give reasons:-
(A) Platinum gold and silver are used to make jewellery.
Answer:-
(I) It not react with air easily
(II)It good conductor of heat
(III) They are less reactive metal
(B) Sodium, potassium and lithium are stored in oil.
Answer:-
(I) They are more reactive metal.
(II) They catch fire easily
(C) Aluminium is highly reactive metal, yet it used to make utensils for cooking.
Answer:-
(I) It is good conductor of heat
(II) It safe for cooking
(D) Carbonate and sulphide ores are usually converted into oxide during the presence of extraction.
Answer:-
(Easily available in internet)
(E) Copper is used to make hotwater tanks and not steel.
Answer:-
(Easily available in internet)
Question 8
While diluting an acid, why is it recommended that acid should be added to water and not water to the acid?
Answer:-
(A) Because beaker becomes very heat.
(B) Beaker will be break
(B) High heat will be released
(D) It may be dangerous
Question 9
(1) A shiny brown coloured element 'X' on heating in air becomes black in colour. Name the element 'X' and the black coloured compound formed. [Write the chemical equations also.]
(2) Identify the substances that are oxidised and the substance that are reduced in the following reactions.
(a) 4Na + O2 ----->. 2Na2O
(b) CuO + H2 ------->. Cu + H20
(3) Why oil and fat containing food items are focused with nitrogen ?
Question 10
Three test tube A,B,C which contain distilled water, acidic solution and basic. If you are given blue litmus paper only, how will you identify each.
Answer:-
(I) First take three stripes of blue litmus paper and dip one in each test tube.
(II) The liquid in test tube A turns blue litmus to red. It means it contains acid.
(III) If other two test tube don't change the colours of blue litmus, it shows that one of them contains a base and other contains distilled water.
(IV) Now put the blue litmus paper which turned red by the acid of test tube A in the remaining two test tube.
(V) If the liquid of test tube B turn that red to blue again,it show that is a base.
(VI) The liquid in C does not turn either blue or red litmus thus is distilled water.
Question 11
Write an equation each for decomposition reaction where energy is supplied in the form of heat,light or electricity.
Answer:'
The decomposition reaction by heat:
The decomposition reaction by light :
The decomposition reaction by electricity :
Question 12
Why are decomposition reaction called the opposite of combination reaction? Write equation for these reactions.
Answer:-
In a combination reaction two or more substances are combined to form new substance while in the decomposition reaction one substance decomposes into two or more substances. Hence, the decomposition reactions are called opposite of combination reactions.
Decomposition reaction CaCO3 (s) ⇨ CaO (s) + CO2 (g)
Combination reaction H2 (g) + Cl2 ⇨ 2HCl (g)
Part-2:-
https://examdeafeat.blogspot.com/2021/04/part-2-important-question-of-class-10.html
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