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MULUNGUSHI UNIVERSITY
SCHOOL OF NATURAL AND APPLIED SCIENCES
DEPT. OF CHEMISTRY AND BIOLOGY
CHE 111 Tutorial Sheet II 2023/2024 Semester I
Question 1
Magnesium hydroxide is prepared by the following reaction below:
Mg (NO 3 ) 2 (aq) + 2KOH (--) 2 KNO 3 (aq) + Mg (OH) 2 (s)
If 25.0 mL of 0.235 M magnesium nitrate are combined with 30.0 mL of 0.260 M potassium hydroxide?
(i) What could the solubility of KOH justify your answer? (ii) Write the ionic equation for the formation of magnesium hydroxide. (iii) What is the mass of magnesium hydroxide formed?
Question 2
9.96g of potassium iodide KI was dissolved in 60.0mL water, then reacted with 20.0 mL of 0.530 M lead (II) nitrate Pb(NO 3 ) 2 according to reaction equation below.
2KI (aq) + Pb (NO 3 ) 2 (aq) 2 KNO 3 (aq) + PbI 2 (s)
(a) Write the ionic equation for the above equation. (b) Calculate the concentration of KI in 60.0 mL water. (c) Determine how much PbI 2 is formed from the above mixture.
Question 3
A compound X has a formula mass of 180.0 g/mol, if one needs to prepare 0.15M of the solution in a 25.0 mL volumetric flask.
(a) What is the mass of compound X is required to prepare the concentration in question? (b) Work out the volume require to prepare a solution of 0.015M in a 250 mL volumetric flask. (c) What is the mass of compound X is in the 0.015M solution in 250 mL volume?
Question 4
To a 2.00 L of 0.445 M HCl solution, you add 3.88 L of a second HCl solution of an unknown concentration. The resulting solution is 0.974 M. Assuming the volumes are additive.
(a) Calculate the moles of HCl in the 0.445 M of 2.0 L. (b) Moles of HCl in a mixture of the solution after mixing. (c) Calculate the molarity of the second HCl solution.
Question 5
Thiosulphate reacts differently with iodine and bromine in the reactions given below:
1# 2S 2 O 32 โ^ + I 2 โ S 4 O 62 โ^ + 2Iโ
2# S 2 O 32 โ^ + Br 2 โ 2SO 42 โ^ + 2Brโ.
(a) Assign the oxidation to elements in each of the two reaction equations above. (b) Identify which substances are acting as oxidizing agent and reducing agent. (c) Separate the reaction equations into two half reactions indicating which is oxidation and reduction.
Question 6
(a) Which of the following arrangements represent increasing oxidation number of the central atom?
(i) CrO 2 โ^ , ClO 3 โ^ , CrO 42 โ , MnO 4 โ
(ii) ClO 3 โ^ , CrO 42 โ^ , MnO 4 โ^ , CrO 2
(b) Explain what is happening to Fluorine and Nitrogen in their respective reactions. (Assign the oxidation number in each case)
(i) 2F 2 + 2OHโ^ โ 2Fโ^ + OF 2 + H 2 O
(ii) 2NO 2 + 2OHโ^ โ NO 2 โ^ + NO 3 โ^ + H 2 O
Question 7
Write balanced chemical equation for the following reactions:
(i) Permanganate ion (MnO 4 โ^ ) reacts with sulphur dioxide gas in acidic medium to produce Mn2+^ and hydrogen sulphate ion (HSO 4 - ).
(ii) Reaction of liquid hydrazine (N 2 H 4 ) with chlorate ion (ClO 3 โ^ ) in basic medium produces nitric oxide (NO) gas and chloride ion (Cl-) in gaseous state.
(iii) Dichlorine heptaoxide (Cl 2 O 7 ) in gaseous state combines with an aqueous solution of hydrogen peroxide ( H 2 O 2 ) in acidic medium to give chlorite ion (ClO 2 โ^ ) and oxygen gas (O 2 ).
Question 8.
Balance the following ionic equations in the medium indicated.
(i) Fe2+^ + Cr 2 O 7 2-^ โ Cr3+^ + Fe3+^ Basic medium (ii) I 2 + NO 3 - โ NO 2 + IO 3 -^ Basic medium (iii) MnO 2 + C 2 O 4 2-^ โ Mn2+^ + CO 2 Acidic medium
