When a salt containing iodide ions is warmed with concentrated sulphuric acid and MnO 2 , iodine is evolved: 2 I - + MnO 2 + 6 H + + 2 SO 4 2 - → I 2 + Mn 2 + + 2 HSO 4 - + 2 H 2 O State which substance is the oxidising agent? Explain your answer.

Consider the oxidation number of each atom in the given redox reaction, 2 I - - 1 + Mn + 4 O 2 - 2 + 6 H + + 1 + 2 S + 6 O 4 - 2 2 - → I 2 0 + Mn 2 + + 2 + 2 H + 1 S + 6 O 4 - 2 - + 2 H 2 + 1 O - 2 The oxidation number of manganese is decreased by 2 units (from + 4 to + 2 ). Therefore, manganese ion is reduced, hence, MnO 2 is the oxidising agent in this reaction.

The compound KBrO 3 decomposes when heated: 2 KBrO 3 → 2 KBr + 3 O 2 State the oxidation number of bromine in KBrO 3 .

The oxidation number of bromine in KBrO 3 can be calculated as given below: The oxidation number of oxygen is - 2 , oxidation number of potassium is + 1 , and the oxidation number of Br be x . We know that, the sum of oxidation numbers of all atoms in a compound is zero. Therefore, for KBrO 3 , 1 × + 1 + x + 3 × - 2 = 0 x = + 5 , hence the oxidation number of Br is + 5 .

The compound KBrO 3 decomposes when heated: 2 KBrO 3 → 2 KBr + 3 O 2 State the oxidation number of bromine in KBr .

The oxidation number of bromine in KBr can be calculated as given below: The oxidation number of potassium is + 1 , and the oxidation number of Br be x . We know that, the sum of oxidation numbers of all atoms in a compound is zero. Therefore, for KBr , 1 × + 1 + x = 0 x = - 1 , hence the oxidation number of Br is - 1 .

The compound KBrO 3 decomposes when heated: 2 KBrO 3 → 2 KBr + 3 O 2 Explain, using oxidation numbers, why this reaction is a redox reaction.

Consider the oxidation number of each atom in the given reaction, 2 K + 1 Br + 5 O 3 - 2 → 2 K + 1 Br - 1 + 3 O 2 0 . The oxidation number of bromine is decreased (from + 5 to - 1 ), hence it is reduced. The oxidation number of oxygen is increased (from - 2 to 0 ), therefore, it is oxidised. Since, the oxidation and reduction reactions are taking place in the same reaction, therefore, it is a redox reaction.

The compound KBrO 3 decomposes when heated: 2 KBrO 3 → 2 KBr + 3 O 2 State the systematic name of KBrO 3 .

Consider KBrO 3 , The oxidation number of K (potassium) is + 1 , and oxidation number of O (oxygen) is - 2 . The oxidation number of Br (bromine) varies. In KBrO 3 , the oxidation number of bromine is + 5 . The ion containing oxygen and bromine is called bromate. The oxidation number comes after the ion, it refers to. Therefore, the full systematic name of KBrO 3 is potassium bromate ( V ).

When KBr reacts with hydrazine, N 2 H 4 , nitrogen gas is evolved. 2 KBrO 3 + 3 N 2 H 4 → 2 KBr + 3 N 2 + 6 H 2 O Deduce the oxidation number change of the bromine atom when KBrO 3 is converted to KBr .

Consider the oxidation number of bromine in the given reaction, 2 K + 1 Br + 5 O 3 - 2 + 3 N 2 H 4 → 2 K + 1 Br - 1 + 3 N 2 + 6 H 2 O The oxidation number of bromine is decreased from + 5 to - 1 , when KBrO 3 is converted to KBr , in the reaction.

When KBr reacts with hydrazine, N 2 H 4 , nitrogen gas is evolved. 2 KBrO 3 + 3 N 2 H 4 → 2 KBr + 3 N 2 + 6 H 2 O Deduce the oxidation number change for each nitrogen atom when N 2 H 4 is converted to N 2 .

Consider the oxidation number of nitrogen in the given reaction, 2 K Br O 3 + 3 N 2 - 2 H 4 + 1 → 2 K Br + 3 N 2 0 + 6 H 2 O The oxidation number of each nitrogen atom is increased from - 2 to 0 , when N 2 H 4 is converted to N 2 , in the reaction.

When KBr reacts with hydrazine, N 2 H 4 , nitrogen gas is evolved. 2 KBrO 3 + 3 N 2 H 4 → 2 KBr + 3 N 2 + 6 H 2 O Explain, using oxidation numbers, why 2 moles of KBrO 3 react with 3 moles of N 2 H 4 ?

Consider the oxidation number of bromine and nitrogen in the given reaction, 2 K + 1 Br + 5 O 3 - 2 + 3 N 2 - 2 H 4 + 1 → 2 K + 1 Br - 1 + 3 N 2 0 + 6 H 2 O The oxidation number of bromine is decreased by 6 units (from + 5 to - 1 ), when KBrO 3 is converted to KBr , in the reaction. Similarly, the oxidation number of each nitrogen atom is increased by 2 units (from - 2 to 0 ), when N 2 H 4 is converted to N 2 , in the reaction. Therefore, the total increase in oxidation number for nitrogen in N 2 H 4 is 2 × 2 = 4 . Thus, to balance the increase in oxidation number to the decrease in oxidation number, in this redox reaction, KBrO 3 must be multiplied by 2 , and N 2 H 4 must be multiplied by 3 , while balancing this reaction. Hence, 2 moles of KBr reacts with 3 moles of N 2 H 4 .

Lawrie Ryan and Roger Norris Solutions for Chapter: Redox Reactions, Exercise 13: EXAM-STYLE QUESTIONS

Author:Lawrie Ryan & Roger Norris

Lawrie Ryan Chemistry Solutions for Exercise - Lawrie Ryan and Roger Norris Solutions for Chapter: Redox Reactions, Exercise 13: EXAM-STYLE QUESTIONS

Attempt the free practice questions on Chapter 7: Redox Reactions, Exercise 13: EXAM-STYLE QUESTIONS with hints and solutions to strengthen your understanding. Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years) solutions are prepared by Experienced Embibe Experts.

Questions from Lawrie Ryan and Roger Norris Solutions for Chapter: Redox Reactions, Exercise 13: EXAM-STYLE QUESTIONS with Hints & Solutions

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 7 - Redox Reactions>EXAM-STYLE QUESTIONS>Q 5

When a salt containing iodide ions is warmed with concentrated sulphuric acid and ${MnO}_{2}$ , iodine is evolved:

$2 I^{-} + {MnO}_{2} + 6 H^{+} + 2 {SO}_{4}^{2 -} \overset{}{\to} I_{2} + {Mn}^{2 +} + 2 {HSO}_{4}^{-} + 2 H_{2} O$

State which substance is the oxidising agent? Explain your answer.

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 7 - Redox Reactions>EXAM-STYLE QUESTIONS>Q 6

The compound ${KBrO}_{3}$ decomposes when heated:

$2 {KBrO}_{3} \overset{}{\to} 2 KBr + 3 O_{2}$

State the oxidation number of bromine in ${KBrO}_{3}$ .

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 7 - Redox Reactions>EXAM-STYLE QUESTIONS>Q 6

The compound ${KBrO}_{3}$ decomposes when heated:

$2 {KBrO}_{3} \overset{}{\to} 2 KBr + 3 O_{2}$

State the oxidation number of bromine in $KBr$ .

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 7 - Redox Reactions>EXAM-STYLE QUESTIONS>Q 6

The compound ${KBrO}_{3}$ decomposes when heated:

$2 {KBrO}_{3} \overset{}{\to} 2 KBr + 3 O_{2}$

Explain, using oxidation numbers, why this reaction is a redox reaction.

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 7 - Redox Reactions>EXAM-STYLE QUESTIONS>Q 6

The compound ${KBrO}_{3}$ decomposes when heated:

$2 {KBrO}_{3} \overset{}{\to} 2 KBr + 3 O_{2}$

State the systematic name of ${KBrO}_{3}$ .

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 7 - Redox Reactions>EXAM-STYLE QUESTIONS>Q 6

When $KBr$ reacts with hydrazine, $N_{2} H_{4}$ , nitrogen gas is evolved.

$2 {KBrO}_{3} + 3 N_{2} H_{4} \overset{}{\to} 2 KBr + 3 N_{2} + 6 H_{2} O$

Deduce the oxidation number change of the bromine atom when ${KBrO}_{3}$ is converted to $KBr$ .

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 7 - Redox Reactions>EXAM-STYLE QUESTIONS>Q 6

When $KBr$ reacts with hydrazine, $N_{2} H_{4}$ , nitrogen gas is evolved.

$2 {KBrO}_{3} + 3 N_{2} H_{4} \overset{}{\to} 2 KBr + 3 N_{2} + 6 H_{2} O$

Deduce the oxidation number change for each nitrogen atom when $N_{2} H_{4}$ is converted to $N_{2}$ .

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 7 - Redox Reactions>EXAM-STYLE QUESTIONS>Q 6

When $KBr$ reacts with hydrazine, $N_{2} H_{4}$ , nitrogen gas is evolved.

$2 {KBrO}_{3} + 3 N_{2} H_{4} \overset{}{\to} 2 KBr + 3 N_{2} + 6 H_{2} O$

Explain, using oxidation numbers, why $2$ moles of ${KBrO}_{3}$ react with $3$ moles of $N_{2} H_{4}$ ?

Lawrie Ryan and Roger Norris Solutions for Chapter: Redox Reactions, Exercise 13: EXAM-STYLE QUESTIONS

Lawrie Ryan Chemistry Solutions for Exercise - Lawrie Ryan and Roger Norris Solutions for Chapter: Redox Reactions, Exercise 13: EXAM-STYLE QUESTIONS

Questions from Lawrie Ryan and Roger Norris Solutions for Chapter: Redox Reactions, Exercise 13: EXAM-STYLE QUESTIONS with Hints & Solutions

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