FRANK Solutions for Class 9 Chemistry Chapter 4 - The Language of Chemistry

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Chapter 4 - The Language of Chemistry Exercise 56

Question 1
What do you understand by the terms symbol and formula?
Solution 1
Symbol - It is the short form or abbreviation used for the name of an element. It represents one atom of that element.
Formula - Formula of a compound represents the composition of a molecule of the substance in terms of the symbols of the elements present in the molecule.
Question 2
Write the formula for the following compounds.
(a) Calcium carbonate
(b) Magnesium sulphate
(c) Ferric sulphate
(d) Calcium bicarbonate
(e) Cuprous iodide
(f) Potassium dichromate
(g) Potassium permanganate
(h) Sodium sulphate
(i) Magnesium nitrate
(j) Calcium phosphate
Solution 2
(a) CaCO3
(b) MgSO4
(c) Fe2 (SO4)3
(d) CaHCO3
(e) CuI
(f) K2Cr2O7
(g) KMnO4
(h) Na2SO4
(i) Mg (NO3)2
(j) Ca3 (PO4)2
Question 3
(a) Define the term valency.
(b) Arrange the following elements in the increasing order of their valencies : phosphorous, helium, carbon, sodium, magnesium.
Solution 3
(a) Valency - The combining capacity of an element is called its valency.
(b) Helium < Sodium < Magnesium < Carbon < Phosphorous
Question 4
Which law govern a completely balanced equation?
Solution 4
Law of conservation of matter governs a completely balanced equation. It states that "matter can neither be created nor destroyed."
Question 5
What does a symbol signify?
Solution 5
A symbol signifies one atom of that element.
Question 6
What are the latin name of iron, tin, lead, sodium, potassium and mercury?
Solution 6
Latin names of the following compounds are-
Iron                     -   Ferrum
Tin                      -   Stannum
Lead                    -   Plumbum
Sodium                -   Natrium
Potassium            -   Kalium
Mercury                -  Hydragyrum
Question 7
What is balanced chemical equation?
Solution 7
The equation in which the total number of atoms of each element in the reactants, on the left side of the equation is same as the number of atoms in the products formed, on the right side of the equation is called as balanced chemical equation.
Question 8
Write down balanced chemical equation, giving as much information as possible, for the following reactions.
(a) A piece of magnesium, when burnt in nitrogen, forms solid magnesium nitride.
(b) A piece of potassium violently reacts with water to form an aqueous solution of potassium hydroxide and to liberate hydrogen.
Solution 8
Frank Solutions Icse Class 9 Chemistry Chapter - The Language Of Chemistry
Question 9
What information is conveyed by a chemical equation?
Solution 9
A chemical equation gives information about-
(i) What substances enter into a given reaction (reactants) and what products are formed as a result of the reaction.
(ii) The  quantities of the reactants and the product formed.
(iii) The  optimum conditions of temperature and pressure.
Question 10
Frank Solutions Icse Class 9 Chemistry Chapter - The Language Of Chemistry
Solution 10
Frank Solutions Icse Class 9 Chemistry Chapter - The Language Of Chemistry
Question 11
What do the symbolsH2, O4 and S mean in the formula H2SO4?
Solution 11
H2 means hydrogen, O4 means oxygen and S means sulphur  in the formula of H2SO4.
Question 12
An element for 'Z' forms an oxide ZO3.
(a) What is the valency of the element Z?
(b) What will be the formula of the fluoride of Z?
Solution 12
(a) The highest valency of the element Z is six.
(b) The formula of the fluoride of Z will be ZF6.
Question 13
An element 'X' forms the following compounds with hydrogen, carbon and oxygen: H2X, CX2, XO2, XO3
State the three valencies of element 'X'. Which are illustrated by these compounds?
Solution 13
The three valencies of element are-
(i) Two-Since the element X combines with two hydrogen to form H2X and two atoms of X combines with one carbon to form CX2.
(ii) Four-Since the element X combines with two oxygen to form XO2.
(iii) Six-Since the element X combines with three oxygen to form XO3.
Question 14
Explain the term variable valency. Why some elements show variable valency, give examples.
Solution 14
Variable valency - Some elements are capable of showing more than one valency in their compounds called variable valency.
Some elements show variable valency i.e. more than one valency since these elements have more than one common valency state.
Question 15
What is a chemical formula? What is the rule for writing a formula correctly?
Solution 15
Chemical formula - It represents the composition of a molecule of the substance in terms of the symbols of the elements present in the molecule. The rule for writing the formula is criss-cross method.
(i) The positive and negative radicals are represented by their symbols and written side by side with the correct valency written below each.
(ii) The valencies are divided by their highest common factor if any to get the simplest ratio.
(iii) These numbers are then interchanged and written as subscripts.
Question 16
Frank Solutions Icse Class 9 Chemistry Chapter - The Language Of Chemistry
Solution 16
Frank Solutions Icse Class 9 Chemistry Chapter - The Language Of Chemistry
Question 17
Name the following compounds:
(a) NaHCO3
(b) Na3Fe(CN)6
(c) Mn3(BO3)2
(d) Ca3(PO4)2
(e) K2MnO4
Solution 17
(a) Sodium hydrogencarbonate
(b) Sodium hexacyanoferrate(III)
(c) Manganese(II) borate
(d) Calcium phosphate
(e) Potassium manganate(VI)
Question 18
What is the difference between Co and CO?
Solution 18
Co stands for cobalt which is an element while CO stands for carbon monoxide which is a compound.
Question 19
What is radical? Give two examples of monovalent and trivalent radicals.
Solution 19
Radical-
A radical is an atom or a group of atoms of same or different elements that behaves in the manner of positive or negative ion. Radicals have their own combining power(valency) and chemical formulae.
Examples-
Monovalent  radicals -H-,OH-,Cl-,NO3-,H+,Na+,K+,NH4+
Trivalent radicals-PO43- ,Fe(CN)63-,AsO3 3-,N3-,Fe3+,Al3+,Bi3+,Au3+
Question 20
What are the modifications made in a chemical equation to overcome the limitations of it in providing information?
Solution 20
Frank Solutions Icse Class 9 Chemistry Chapter - The Language Of Chemistry
Question 21
What do you understand by (a) Anion, (b) Cation ?
Solution 21
(a) Anion - Negatively charged radicals are termed as anions.
(b) Cation - Positively charged radicals are termed as cations.
Question 22
What are the disadvantages associated with hit and trial method of balancing the equations.
Solution 22
Disadvantages associated with hit and trial method of balancing of equations-
(i) It is tedious and takes a long time.
(ii) The method is rather difficult for balancing such equations which contain the same element being repeated in a number of compounds.
(iii) It does not give any information regarding the mechanism of the reaction.