Language of Chemistry Dalal Simplified ICSE Class-9 Solutions

Language of Chemistry Dalal Simplified ICSE Class-9 Solutions Chapter-1 . Therefore we Provide Step by Step Solutions of Exercise/Lesson -1 The Language of Chemistry with Additional Questions and Unit Test of Dr Viraf J Dalal Middle School Chemistry Allied Publishers. Visit official Website CISCE for detail information about ICSE Board Class-9.

The Language of Chemistry Dalal Simplified Class-9 ICSE Chemistry Chapter-1

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Previous Year Question

Additional Questions

Unit Test Questions

Language of Chemistry Questions Previous Year

Question.1 (1985)

XCl₂ is the chloride of a metal X. State the formula of the sulphate and the hydroxide of the metal X.
Answer

Question.1 (1987)

An element X is trivalent. Write the balanced equation for the combustion of X in oxygen.
Answer:
Combustion of X³⁺ in oxygen means oxide of X

Question.1 (1991)

The formula of the nitride of a metal X is XN, state the formula of :

its sulphate
its hydroxide.

Answer:
Formula of nitride of metal X is XN
Since valency of nitrogen is 3-
∴ Valency of X is 3+

Question.1 (1992)

What is the valency of nitrogen in :

NO
N₂O
NO₂

Answer:

Additional Questions of Language of Chemistry Dalal Simplified Class-9

Question 1.

What is meant by the term ‘symbol’. Give the qualitative and quantitative meaning of the term ‘symbol’.
Answer:
Symbol : “Is the short form that stands for the atom of a specific element.”
Qualitative meaning : C is the symbol of atom of element carbon
S is the symbol of atom of element sulphur.
This means symbol stand for a specific element.
No two elements can have the same symbol.
Quantitative meaning : A symbol also represents quantity of the element i.e. atomic mass of element. Symbol C represents 12 g of carbon. In other words how many times that element is heavier than 1/12 th C¹²

Question 2.

Name three metals whose symbols are derived from :

(a) the first letter of the name of the element
(b) from their Latin names.

Answer:

Question 3.

Explain the meaning of the term ‘valency’.
State why the valency of the metal potassium is +1 and of the non-metal chlorine is -1.
Answer:
Valency : “Is the combining capacity of atom or of a radical.” OR
“Valency is the number of electrons, which an atom can lose/gain/share during a chemical reaction.”
Metal potassium (K) has 1 electron in outer most shell which it loses and becomes K+ has valency [+1] whereas
Non-metal chlorine [Cl] has 7 electrons in valence shell and gains 1 electron and becomes [Cl^–] has valency [-1]

Question 4.

What is meant by the term ‘variable valency’. Give a reason why silver exhibits a valency of +1 and +2.
Answer:
Variable valency : “Certain elements exhibit more than one valency and show variable valency.”
Reason : Why silver exhibits valency +1 and +2 Ag 47 [2, 8, 18, 18, 1] has 1 electron in the outermost shell when loses this electron shows [+1] valency but when penultimate shell has not attained stability and one more electron jumps to the outermost shell there by increasing valency electron and new configuration [2, 8, 18, 17, 2] loses two electrons and has valency [+2]
∴ Silver exhibits Ag¹⁺ [ous] and Ag²⁺ [ic]

Question 5.

Give examples of eight metals which shows variable valency. State the valency of sulphur in :

(a) SO₂
(b) SO₃

Answer:
Eight metals which show variable valency are

Question 6.

State the valency in each case and name the following elements or radicals given below

………………………..

Answer:

Question 7.

State the variable valencies of the following elements and give their names.
(a) Cu, (b) Ag, (c) Hg, (d) Fe, (e) Pb, (f) Sn, (g) Mn, (h) Pt, (i) Au
Answer:

Question 8.

State which of the following elements or radicals are divalent –
(a) Lithium, (b) Nickel, (c) Ammonium, (d) Bromide, (e) Sulphite, (f) Nitride, (g) Carbide, (h) Chromium, (i) Bisulphite, (j) Dichromate, (k) Permanganate.
Answer:

(b) Nickel
(e) Sulphite
(j) Dichromate are divalent

Question 9.

Explain the meaning of the term ‘compound’ with a suitable example. State the main characteristics of a compound with special reference to the compound iron [II] sulphide.
Answer:
Compound : “Is a pure substance made up of two or more elements combined chemically by in a fixed proportion.”
Example : CO₂ carbon dioxide is made up of two elements carbon and oxygen C,
12 parts by weight and oxygen
2 × 16 = 32 parts by weight
i.e. in ratio C : O = 12 : 16 = 3 : 4

CHARACTERISTICS OF COMPOUND :

Components in definite proportion e.g. compound iron [II] sulphide FeS element Iron and sulphur are in definite ratio.
Compound is Homogeneous.
Particles in a compound are of J kind composition of iron (II) sulphide is uniform and components cannot be seen separately.
Compound has definite set of properties.
Component in FeS do not retain their original properties, i.e. iron cannot be attracted by a magnet, sulphur is insoluble in CS₂ and Fe does not giyes H₂ with dil. acid. This means compound formed has new properties.

Question 10.

Name the elements in the compound and give the formula – of the following compounds :
(a) Nitric acid, (b) Carbonic acid, (c) Phosphoric acid, (d) Acetic acid, (e) Blue vitriol, (f) Green vitriol, (g) Glauber’s salt, (h) Ethane, (i) Ethanol

Answer:

Question 11.

Explain the term ‘chemical formula’. State why the molecular formula of zinc carbonate is ZnCO₃
Answer:
Chemical Formula : “A molecule of a substance element or compound could be represented by symbols. Representation known as chemical formula i.e. molecular formula of oxygen gas is O₂ water H₂O, hydrochloric acid HCl etc.
Molecular formula of zinc carbonate : Zinc and carbonate both have valency

Question 12.

Write the formula of the following compounds :

…………………………..

Answer:

Question 13.

Write the names of the following compounds :

……………………………

Answer:

Question 14.

Explain the term ‘chemical equation’. What is meant by ‘reactants’ and ‘products’ in a chemical equation.
Answer:
Chemical equation : “Is the symbolic representation of a chemical reaction using symbols and the formulae of the substances involved in the reaction.”
Sulphur bums in oxygen is a chemical reaction and sulphur dioxide is formed. This can be represented as sulphur + oxygen → sulphur dioxide is word equation

Reactants : Substances taking part in a reaction separated by (+) sign on the left hand side of arrow are called reactants.
Products : Substances formed in the reaction are called products.

Question 15.

Give an example of a chemical equation in which two reactants form –

(a) one product
(b) two products
(c) three products
(d) four products

Answer:

Question 16.

…………..

(a) State what is a ‘balanced equation’.
(b) Give a reason why the above equation is balanced.
(c) State why the compound MnO₂ is written above the arrow.

Answer:

(a) Balanced equation : “Equation in which the total number of atoms of each element in the reactants, on the left side of the equation is equal to the number of atoms of each element in the products formed, on the right side of the equation.”
(b) As the total number of [K, Cl, 0] atoms on the L.H.S. is equal to the number of the given atoms on the R.H.S., the given equation is balanced.
(c) MnO₂ is a catalyst in the reaction which does not under go any change and simply increases the rate of reaction is written above the arrow.

Question 17.

What do the symbols ……

Answer:

Question 18.

…………..

(a) State the information provided by the above chemical equation.
(b) State the information not conveyed by the above chemical equation.

Answer:

(a) Information provided by equation

Calcium carbonate reacts with [dil.] hydrochloric acid to produce calcium chloride, water and Carbondioxide.
One molecule of calcium carbonate reacts with two molecules of acid to produce one molecule of calcium chloride, one molecule of water and one molecule of carbondioxide.
About the chemical composition of respective, molecules like one molecule of calcium chloride contains one atom of calcium, one atom of carbon and three atoms of oxygen.
Molecular masses
that 100 parts by weight of calcium carbonate reacts with 73 parts by weight of hydrochloric acid to produce 111 parts by weight of calcium chloride 18 parts by weight of water and 44 parts by weight of carbon dioxide.
That reaction is irreversible.
That about the state of substances present i.e. solid, liquid or gas.

(b) Information not conveyed are :

Time, reaction takes to complete.
About the concentrations of reactants and products.
Speed of reaction.
Changes in colour occuring – during the reaction.
Whether heat is given out or absorbed during the reaction.
The physical state of reactants and products.

Question 19.

Balance the following simple equation :

……………

Answer

Question 20.

Write balanced equations for the following word equations :

Potassium nitrate → Potassium nitrite + Oxygen
Calcium + Water → Calcium hydroxide + Hydrogen
Iron + Hydrochloric acid → Iron [II] chloride + Hydrogen
Nitrogen dioxide + Water + Oxygen → Nitric acid
Lead dioxide [lead (IV) oxide] → Lead monoxide + Oxygen
Aluminium + Oxygen → Aluminium oxide
Iron + Chlorine → Iron [III] chloride
Potassium bromide + Chlorine → Potassium chloride + Bromine
Potassium bicarbonate → Potassium carbonate + Water + Carbon dioxide
Calcium hydroxide + Ammonium chloride → Calcium chloride + Water + Ammonia

Answer:

Question 21.

Balance the following important equations

……………………

Answer:

Ans 21 Additional Question The Language Of Chemistry ICSE Dalal Simplified Chemistry

Question 22.

Give balanced equations for (1) & (2) by partial equation method, [steps are given below]
(1) Reaction of excess ammonia with chlorine – Ammonia as a reducing agent

(a) Ammonia first reacts with chlorine to give hydrogen chloride and nitrogen.
(b) Hydrogen chloride then further reacts with excess ammonia to give ammonium chloride.

(2) Oxidation of Lead [II] Sulphide by Ozone

(a) Ozone first decomposes to give molecular oxygen & nascent oxygen.
(b) Nascent oxygen then oxidises lead [II] sulphide to lead [II] sulphate.

Answer:

(1)

(a) Ammonia reacts with chlorine to give hydrogen chloride and nitrogen.
(b) Hydrogen chloride reacts with excess ammonia to give ammonium chloride.

Question 23.

Define the terms – (a) Relative atomic mass (b) Relative molecular mass. State why indirect methods are utilised to determine the absolute mass of an atom. Explain in brief the indirect method used.
Answer:
(a) Relative atomic mass [RAM] of an element :
“is the number of times one atom of an element is heavier than 1/12 the mass of an atom of carbon [C¹²]”
or
“Mass of an atom of an element as compared with 1/12 mass of an atom of carbon [C¹²]”
(b) Relative molecular mass [RMM] of an element/compound : “Is the number of times one molecule of the substance is heavier than 1/12 the mass of an atom of carbon [C¹²].

To determine the absolute mass of an atom indirect methods are utilised as Atom are extremely small and very light.
An isotope of carbon C¹² [carbon -12 atom] has been assigned atomic mass of exactly 12 atomic mass unit] is used.

Question 24.

1. Calculate relative molecular mass of

(a) ZnCO₃
(b) CaSO₄ [Zn = 65, S=32, O = 16, Ca = 40, C = 12]

2. Calculate the percentage composition of

(a) calcium chloride
(b) calcium nitrate [Ca = 40 , Cl = 35.5 , N = 14 , O = 16]

Answer: