Name: Valencies of Some Common Ions
Uploaded: 2019-07-19
Duration: 4 min 56 s
Description: Ionic compounds are composed of positively charged and negatively charged ions. Do you know what the charges on these ions are called? Let’s find out in this...

Question

How are the limitations or drawbacks of a chemical equation removed?

Accepted Answer

Some drawbacks of chemical equation can be removed as follows.
(i) The physical states of the reactants and products can be indicated by using the symbol, i.e, s for solid, l for liquids, g for gases and aq for aqueous solutions.
$e . g ., Zn (s) + 2 HCl (aq) \to {ZnCl}_{2} (aq) + H_{2} (g)$

(ii) The conditions necessary for the reaction to occur are represented by words, formula or symbol above the arrow between the reactants and products.
$∆ e . g ., Fe (s) + S (s) \to FeS (s)$

(iii) The concentration of the solution of the reactants can be shown by writing dil. for dilute and conc. for concentrated solution.
$∆ e . g ., Cu (s) + 2 H_{2} {SO}_{4} (conc .) \to {CuSO}_{4} (aq) + {SO}_{2} (g) + 2 H_{2} O (l)$

(iv) The heat changes during a reaction are indicated by writing $+ Q kJ or - Q kJ$ along with the products for exothermic and endothermic reactions respectively. $e . g ., 2 H_{2} (g) + O_{2} (g) \to 2 H_{2} O (l) + 572 kJ C (s) + H_{2} O (g) \to CO (g) + H_{2} (g) - 131 kJ$

(v) The evolution of a gas can be indicated by writing arrow pointing upwards $(↑)$ .
$e . g ., Zn (s) + H_{2} {SO}_{4} (aq) \to {ZnSO}_{4} (aq) + H_{2} (g) ↑$

(vi) The formation of a precipitate is indicated by writing an arrow pointing downwards $(↓)$ below the formula of the product.
$e . g ., {AgNO}_{3} (aq) + NaCl (aq) \to AgCl (s) ↓ + {NaNO}_{3} (aq) (ppt .)$

(vii) In case of reversible reaction, double-headed arrows $(⇌)$ are put between the reactants and products.
$e . g ., N_{2} (g) + O_{2} (g) \overset{3000^{0} C}{⇆} 2 NO (g)$

(viii)The rate of reaction can be shown by writing slow or fast along with the products.
$e . g ., 2 NO + O_{2} (g) \to 2 {NO}_{2} (g) (Fast) 2 CO + O_{2} (g) \to 2 {CO}_{2} (g) (Slow)$

How are the limitations or drawbacks of a chemical equation removed?

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