# Chem MC analysis. In which of the following cases may it obtain a complete neutralization? (1)25.0 cm3 of 0.120 M sulphuric acid and 50cm3of 0.120M sodium hydroxide solution (2)50.cm3 of 0.5 M Sodium hydroxide and 0.025 moles of aqueous ammonium chlorid

Chemistry                                       4A Ivan Liu Chun Pok (12)

Mc analysis

Topics: Neutralization, Reaction between alkali and ammonium compound,

Strength of Acid and Alkali, Reacting Masses, Volumetric Analysis

In which of the following cases may it obtain a complete neutralization?

(1)25.0 cm3 of 0.120 M sulphuric acid and 50cm3of 0.120M sodium hydroxide solution

(2)50.cm3 of 0.5 M Sodium hydroxide and 0.025 moles of aqueous ammonium chloride

(3)20.0cm3 of 0.100M phosphoric acid and 30.0cm3 of 0.200 M potassium hydroxide solution

(4)Dissolve 0.2025g of solid sodium hydroxide in water and make up to 250cm3 of solution, then 25.0cm3 of this solution is added to 50.0cm3 of 1M hydrochloric acid

A.2

B.1, 3

C.3, 4

D.1, 2, 4

Option 1:

H2SO4(aq) + 2NaOH(aq)→ Na2SO4(aq) +H2O(l)

Mole ratio of H2SO4 : NaOH = 1:2

Using the formula,

Molarity of a solution M or mol dm-3

= Number of moles of solute (mol) / Volume of solution (dm3)

Number of moles of solute (mol)

= Molarity of a solution M or mol dm-3X Volume of solution (dm3)

Number of moles of H2SO4 given: 0.12 X (25.0 /1000)

= 0.003mol

Number of moles of NaOH given: 0.12 X (50.0/1000)

= 0.006mol

Mole ratio of H2SO4 : NaOH = 0.003 /0.006 = 1:2

Therefore, option (1) is correct.

Option 2 :

NaOH(aq) + NH4Cl (aq)→ NaCl(aq)+ NH3(g) + H2O(l)

Mole ratio of NaOH : NH4Cl = l :1

Using the formula,

Molarity of a solution M or mol dm-3

= Number of moles of solute(mol) / Volume of solution (dm3)

Number of moles of solute(mol)

= Molarity of a solution M or mol dm-3X Volume of solution (dm3)

Number of moles of NaOH given: 0.5X (50/1000)

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***** Clear, step by step calculations and analyses of the four reactions. The author demonstrates a detailed understanding of the chemistry involved and possible pitfalls.