Answer to Question #189067 in General Chemistry for dani

Question

Assignment 2, Mark:  (10 %)

1. Consider the titration of Fe⁺² (0.02M, 50 ml) with standard Ce⁺⁴ (0.05M) monitored potentiometrically with Pt electrod, where reduction of Fe⁺² and Ce⁺³ occurs and SHE as a reference electrode. Calculate the potential change of the cell after 20 and 25 ml of Ce⁺⁴ additions.

2. In comparison of two methods for the determination of chromium in rye grass the following result were obtained: method 1: Mean = 1.48, Sd = 0.28, N=5; Method 2: Mean = 2.33; Sd = 0.31, N=5. The pooled standared diviation is given by Sp = 0.295.

A. Is there any significance difference between the two means?

3. 2.560 g of impure copper (II) sulphate sample was dissolved in water and precipitated with excess sodium hydroxide solution. If 1.245 g copper (II) hydroxide was obtained, what is the percentage of copper (II) sulphate in the impure sample? (Mwt; Cu = 63 g/mol, S = 32g/mol, O=16g/mol, Fe =56 g/mo

Answer 1

1)Potential Change =2.37V

2)Yes

3)Percentage of Copper (II) sulphate in the impure sample=67.2%