Page 26 - Chemistry ICSE Class IX

14 ICSE Chemistry – 9
Solution:

Compounds Ions present Formula
2+
(a) Magnesium chloride Mg 02 Cl 1– MgCl 2
2+
(b) Calcium oxide Ca 02 O 2– Ca O Ÿ CaO
2
2
(c) Copper nitrate Cu 02 NO 3 1– Cu(NO )
2+
3 2
(d) Aluminium chloride Al 02 Cl 1– AlCl 3
3+
(e) Calcium carbonate Ca 02 CO 2– Ca (CO ) Ÿ CaCO 3
2+
2
3 2
3
ASSIGNMENT 2
Molecule, Molecular formula, Writing of chemical formulae
ϭ͘ tŚĂƚ ŝƐ ŵĞĂŶƚ ďLJ ŵŽůĞĐƵůĂƌ ĨŽƌŵƵůĂ͍
Ϯ͘ tƌŝƚĞ ƚŚĞ ŶĂŵĞƐ ĂŶĚ ĨŽƌŵƵůĂĞ ŽĨ ƚǁŽ ƚƌŝĂƚŽŵŝĐ ŵŽůĞĐƵůĞƐ͘
ϯ͘ tƌŝƚĞ ƚŚĞ ĐŚĞŵŝĐĂů ĨŽƌŵƵůĂĞ ŽĨ ƚŚĞ ĨŽůůŽǁŝŶŐ͗
^ŝůǀĞƌ ŝŽĚŝĚĞ͕ ĂůĐŝƵŵ ĐŚůŽƌŝĚĞ͕ ,LJĚƌŽŐĞŶ ƐƵůƉŚŝĚĞ͕ WŚŽƐƉŚŽƌƵƐ ƚƌŝŽdžŝĚĞ͘
ϰ͘ tŚĂƚ ŝƐ ƚŚĞ ƐƚŽŝĐŚŝŽŵĞƚƌŝĐ ĨŽƌŵƵůĂ ĨŽƌ͕
;ĂͿ ĨĞƌƌŝĐ ĐĂƌďŽŶĂƚĞ ;ďͿ njŝŶĐ ƉŚŽƐƉŚĂƚĞ
ϱ͘ dŚĞ ǀĂůĞŶĐŝĞƐ Žƌ ĐŚĂƌŐĞƐ ŽŶ ƐŽŵĞ ŝŽŶƐ ĂƌĞ ŐŝǀĞŶ ďĞůŽǁ͗
ŝŶĐ ŝŽŶ͕ Ϯн͖ WŚŽƐƉŚĂƚĞ ŝŽŶ͕ ϯʹ͖ EŝƚƌŽŐĞŶ͕ ϯн͖ ^ŽĚŝƵŵ ŝŽŶ͕ ϭн͖ KdžLJŐĞŶ͕ Ϯʹ͖ ƌŽŵŝĚĞ ŝŽŶ ϭʹ͖ >ĞĂĚ ŝŽŶ͕ Ϯн͖
hƐŝŶŐ ƚŚĞ ĂďŽǀĞ ŝŶĨŽƌŵĂƟŽŶ͕ ǁƌŝƚĞ ĚŽǁŶ ƚŚĞ ĐŚĞŵŝĐĂů ĨŽƌŵƵůĂĞ ŽĨ ĂŶLJ ƚǁŽ ŽĨ ƚŚĞ ĨŽůůŽǁŝŶŐ͗
;ĂͿ ŝŶĐ ƉŚŽƐƉŚĂƚĞ ;ďͿ EŝƚƌŽŐĞŶ ŽdžŝĚĞ ;ĐͿ ^ŽĚŝƵŵ ƉŚŽƐƉŚĂƚĞ ;ĚͿ >ĞĂĚ ďƌŽŵŝĚĞ͘

Chemical Equation

What is a chemical equation

During a chemical reaction, certain substances react together to form some
new substances. A reaction is described in terms of the names and quantities
of the reactants and products. For example, the chemical reaction during
the burning of carbon (or coal) may be described by the statement, “ECTDQP
KU DWTPV KP GZEGUU QH CKT QT QZ[IGP VQ RTQFWEG ECTDQP FKQZKFG”. This reaction
may also be described by a worded equation, XK\.,
Carbon + Oxygen (excess) o Carbon dioxide
Such worded equations are long and not convenient for describing
chemical reactions. These long worded equations can be shortened by
using symbols and formulae of the substances involved in the reaction.
For example, the reaction of zinc metal with dilute sulphuric acid to
produce zinc sulphate and hydrogen may be written as,
Zinc (metal) + dil. Sulphuric acid o Zinc sulphate + Hydrogen
This worded equation may be written in terms of symbols and
formulae as,
Zn + dil. H SO o ZnSO 4 + H 2
4
2
dŚĞ ƚǁŽ ƐŝĚĞƐ ;ƌĞĂĐƚĂŶƚƐ ĂŶĚ Thus, Zn + dil. H SO o ZnSO + H is the chemical equation for
4
4
2
ƉƌŽĚƵĐƚƐͿ ĂƌĞ ƐĞƉĂƌĂƚĞĚ ĞŝƚŚĞƌ ďLJ Ă the reaction between zinc and sulphuric acid. 2
ƐŝŐŶ ŽĨ ĞƋƵĂůŝƚLJ ;сͿ Žƌ ƚŚĂƚ ŽĨ ĂŶ ĂƌƌŽǁ
(oͿ ƉŽŝŶƟŶŐ ƚŽǁĂƌĚƐ ƉƌŽĚƵĐƚƐ͘ &Žƌ Ă A shorthand representation of a chemical reaction in terms of
ƌĞǀĞƌƐŝďůĞ ƌĞĂĐƟŽŶ͕ Ă ƐŝŐŶ ;qͿ ŝƐ ƵƐĞĚ symbols and formulae of the substances involved is called a chemical
ŝŶ ƉůĂĐĞ ŽĨ ƚŚĞ ĂƌƌŽǁ ;oͿ͘ equation.