FRANK Solutions for Class 9 Chemistry Chapter 4 - The Language of Chemistry
Chapter 4 - The Language of Chemistry Exercise 56
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.
(a) What is the valency of the element Z?
(b) What will be the formula of the fluoride of Z?
(b) The formula of the fluoride of Z will be ZF6.
State the three valencies of element 'X'. Which are illustrated by these compounds?
(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.
Some elements show variable valency i.e. more than one valency since these elements have more than one common valency state.
(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.
(b) Sodium hexacyanoferrate(III)
(c) Manganese(II) borate
(d) Calcium phosphate
(e) Potassium manganate(VI)
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.
Monovalent radicals -H-,OH-,Cl-,NO3-,H+,Na+,K+,NH4+
Trivalent radicals-PO43- ,Fe(CN)63-,AsO3 3-,N3-,Fe3+,Al3+,Bi3+,Au3+
(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
(c) Fe2 (SO4)3
(i) Mg (NO3)2
(j) Ca3 (PO4)2
(b) Cation - Positively charged radicals are termed as cations.
(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.
(b) Arrange the following elements in the increasing order of their valencies : phosphorous, helium, carbon, sodium, magnesium.
(b) Helium < Sodium < Magnesium < Carbon < Phosphorous
Iron - Ferrum
Tin - Stannum
Lead - Plumbum
Sodium - Natrium
Potassium - Kalium
Mercury - Hydragyrum
(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.
(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.
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