Chemistry 2019 Solved Paper Previous Year Question ICSE

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Chemistry 2019 Solved Paper Previous Year Question

(Two hours)

Answers to this Paper must be written on the paper provided separately.

You will not be allowed to write during the first IS minutes.

This time is to be spent in reading the Question Paper.

The. time given at the head of this paper is the time allowed for writing the answers.

Section I is compulsory. Attempt any four questions from Section II.

The intended marks for questions or parts of questions are given in brackets [ ].

Previous Year Solved Question Paper Chemistry 2019

Section -1 [40 Marks]

(Attempt all questions from this Section)

Question 1.

(a) Choose the correct answer from the options given below: [5]

(i) An electrolyte which completely dissociates into ions is :

(A) Alcohol
(B) Carbonic acid
(C) Sucrose
(D) Sodium hydroxide

(i)  (D) Sodium hydroxide

(ii) The most electronegative element from the following elements is :

(A) Magnesium
(B) Chlorine
(C) Aluminium
(D) Sulphur

(B) Chlorine

(iii) The reason for using Aluminium in the alloy duralumin is:

(A) Aluminium is brittle
(B) Aluminium gives strength
(C) Aluminium brings lightness
(D) Aluminium lowers melting point

(C) Aluminium brings lightness

(iv) The drying agent used to dry HCl gas is :
(A) Cone. H2SO4
(B) ZnO
(C) Al2O3
(D) CaO

(A) Cone. H2SO4

(v) A hydrocarbon which is a greenhouse gas is :
(A) Acetylene
(B) Ethylene
(C) Ethane
(D) Methane

(D) Methane

(b) Fill in the blanks with the choices given in brackets: [5]

(i) Conversion of ethanol to ethene by the action of concentrated sulphuric acid is an example of ……………..
(dehydration / dehydrogenation / dehydrohalogenation)

dehydration

(ii) When sodium chloride is heated with concentrated sulphuric acid below 200°C, one of the products formed is ………………
(sodium hydrogen sulphate / sodium sulphate / chlorine)

sodium hydrogen sulphate

(iii) Ammonia reacts with excess chlorine to form ………………..
(nitrogen / nitrogen trichloride / ammonium chloride)

nitrogen trichioride

(iv) Substitution reactions are characteristic reactions of ……………..
(alkynes / alkenes / alkanes)

alkanes

(v) In Period 3, the most metallic element is ……………..
(sodium / magnesium / aluminium)

sodium

(c) Write a balanced chemical equation for each of the following reactions: [5]

(i) Reduction of copper (II) oxide by hydrogen.

CuO+H→ Cu+H2O

(ii) Action of dilute sulphuric acid on sodium hydroxide

.

2NaOH + H2S04 → Na2SO4 + 2H2O

(iii) Action of dilute sulphuric acid on zinc sulphide.

ZnS + H2SO4 → ZnSO4 + H2S

(iv) Ammonium hydroxide is added to ferrous sulphate solution.

FeSO4 + 2NH40H → (NH4)SO4 + Fe(OH)2

(v) Chlorine gas is reacted with ethene.

(d) State one observation for each of the following: [5]

(i) Concentrated nitric acid is reacted with sulphur.

Dense brown fumes of nitrogen dioxide gas will be released

(ii) Ammonia gas is passed over heated copper (II) oxide.

The black colour copper oxide will change to reddish pink copper.

(iii) Copper sulphate solution is electrolysed using copper electrodes.

When copper sulphate solution is electrolysed using copper electrodes, reddish pink deposit of copper metal takes place on cathode.

(iv) A small piece of zinc is added to dilute hydrochloric acid.

Zn + 2HCl > ZnCl2 + H2
Zinc metal dissolves forming solution with the liberation of hydrogen gas which bums with blue flame and gets extinguished with pop sound.

(v) Lead nitrate is heated strongly in a test tube.

White powder of lead nitrate decompose to form yellow coloured lead oxide and liberating dense brown fumes of nitrogen dioxide gas.

(e) (i) Calculate: [5]

1. The number of moles in 12 g of oxygen gas. [O = 16] 2. The weight of 1022 atoms of carbon.
[C = 12, Avogadro’s No. = 6 × 1023]

1. Oxygen gas (O2)
Molecular mass = 16 x 2 = 32 g
32 g of oxygen gas → 1 mole
1 g of oxygen gas → $\frac { 1 }{ 32 }$ mole
12 g of oxygen gas → $\frac { 1 }{ 32 }$ × 12mole = 0.375 mole

2. 6.022 x 1023 atoms of carbon weigh → 12 g
1 atom of carbon weighs → $\frac{12}{6 \times 10^{23}}$
1022 atoms of carbon will weigh → $\frac{12}{6 \times 10^{23}} \times 10^{22}=\frac{12}{60}=\frac{1}{5}$ = 0.2 g

(ii) Molecular formula of a compound is C6H18O3. Find its empirical formula.

Molecular formula = C6H18O3
Take the common multiple
Molecular formula = (C2H60)3
Molecular formula = (Empirical formula)„
Thus, empirical formula = C2H6O

(f) (i) Give the IUPAC name of the following organic compounds: [5]
1.
2.

1. Prop – 1 – yne or propyne
2. Ethanal

(ii) What is the special feature of the structure of ethyne ?

Ethanal

Special feature of the structure of ethyne is the presence of triple bond.

(iii) Name the saturated hydrocarbon containing two carbon atoms.

Ethane

(iv) Give the structural formula of Acetic acid

Acetic acid (CH3COOH)

(g) Give the appropriate term defined by the statements given below: [5]

(i) The formula that represents the simplest ratio of the various elements present in one molecule of the compound.

Empirical formula

(ii) The substance that releases hydronium ion as the only positive ion when dissolved in water.

Acid

(iii) The tendency of an atom to attract electrons totvards itself when combined in a covalent compound.

Electronegativity

(iv) The process by which certain ores, specially carbonates, are converted to oxides in the absence of air.

Calcination

(v) The covalent bond in-which the electrons are shared equally between the combining atoms.

Non-polar covalent bond

(h) Arrange the following according to the instructions given in brackets : [5]
(i) K, Pb, Ca, Zn. (In the increasing order of the reactivity)

Pb < Zn < Ca < K
(According to the position in reactivity series)

(ii) Mg2+, Cu2+, Na1+, H1+ (In the order of preferential discharge at the cathode)