Waec Chemistry practical answers 2023

Waec Chemistry practical answers 2023

Here is the Waec Chemistry practical answers 2023

Answers

(3b)

One possible chemical test to distinguish between dilute HCl and dilute HNO3 is to use silver nitrate (AgNO3) solution.

When a few drops of dilute HCl are added to a solution of AgNO3, no visible reaction occurs. However, when a few drops of dilute HNO3 are added to a solution of AgNO3, a white precipitate of silver chloride (AgCl) is formed.

The relevant equation for the reaction between dilute HNO3 and silver nitrate is:

HNO3 + AgNO3 -> AgCl + HNO3

The formation of the white precipitate of silver chloride indicates the presence of HNO3, while the absence of any reaction indicates the presence of HCl.
(3a)

To determine the volume of water that should be added, we can use the formula for dilution:

M1V1 = M2V2

Where:
M1 = initial molarity of the solution
V1 = initial volume of the solution
M2 = final molarity of the solution
V2 = final volume of the solution

Given:
M1 = 0.5 mol/dm³
V1 = 100 cm³ (or 0.1 dm³)
M2 = 0.3 mol/dm³
V2 = ? (volume of water to be added)

Rearranging the formula, we have:
V2 = (M1 * V1) / M2

Substituting the given values, we get:
V2 = (0.5 mol/dm³ * 0.1 dm³) / (0.3 mol/dm³)
= (0.05 mol) / (0.3 mol/dm³)
= 0.1667 dm³

Therefore, approximately 0.1667 dm³ (or 166.7 cm³) of water should be added to 100 cm³ of 0.5 mol/dm³ HCl in order to obtain 0.3 mol/dm³ HCl.
(2)

(a) Observation: G dissolves completely in distilled water.
Conclusion: G is soluble in water.
(b)
(i) Observation: The litmus paper remains unchanged.
Conclusion: The solution is neutral, indicating that G is neither acidic nor basic.
(ii) Observation: The solution turns cloudy.
Conclusion: G reacts with NaOH to form a precipitate.
(iii) Observation: No visible reaction occurs.
Conclusion: G does not react with dilute HNO3.
(iv) Observation: A white precipitate forms.
Conclusion: G reacts with BaCl2 to form a precipitate in the presence of excess dilute HNO3.