- No. iv. Differentiate between ‘p’ and pH
Answer. ‘p’ before any symbol means negative logarithm of the symbol. i.e, taking the common logarithm of the figure and multiplying it with-1.
While pH is also the negative logarithm of molar concentration of the hydrogen ions. Such as;
- No. i. How the salts are named?
Answer. Salts get their name from the name of the metal and the acid from which they are made of sodium (Na) reacts with hydrochloric acid (HC1) to give sodium chloride (NaCl) salt, similarly zinc (Zn) metal reacts with sulphuric acid (H2SO4) to form zinc sulphate (ZnSO4) salt.
- No. ii. Name the salts which are formed when Zn metal reacts with following acids. a. nitric acid b. phosphoric acid c. acetic acid
Answer. When Zn metal reacts with nitric acid it will form zinc nitrate
4HNO3(aq) + Zn(s) ——— > Zn(NO3)2(aq) + 2NO2 (g) + 2NO2 (g)
When it reacts with phosphoric acid it will form zinc phosphate
2H3 PO4(aq) + 3Zn(s) —————> Zn3 (PO4) 2(aq) + 3H2(g)
When it reacts with acetic acid it will form zinc acetate
2CH3COOH(aq) + Zn(s) Zn(CH3COO)2(aq) + 2H2(aq)
- No. iii. How will you justify salts are neutral compounds?
Answer. Salts are made up of positive ions (cations) and negative ions (anions). Mostly salts consist of equal number of cations and anions therefore, they are neutral for example NaCl, CaCO3, MgSO4 etc.
But majority of the salts do not compose of equal number of positive and negative ions such as CaCl2, Aids, Na2SO4, Ca (HCO3)2 etc. These salts are also neutral because they have equal number of positive and negative charge. For example in case of CaCl2. It consist of 1 ion of Ca having +2 charge and 2 ion of Cl having -1 charge
Total positive charges are 1 x +2 = + 2
Total negative charges are 2 x – l = – 2
A total positive charge are equal to total negative charges hence salt is neutral.