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The compound chlorine dioxide, ClO2, can be prepared by the reaction shown. - CIE - A-Level Chemistry - Question 1 - 2017 - Paper 1
Question 1
The compound chlorine dioxide, ClO2, can be prepared by the reaction shown.. NaClO2 + Cl2 → ClO2 + NaCl (a) Using oxidation numbers, explain why this reaction is ... show full transcript
Worked Solution & Example Answer:The compound chlorine dioxide, ClO2, can be prepared by the reaction shown. - CIE - A-Level Chemistry - Question 1 - 2017 - Paper 1
Step 1
Using oxidation numbers, explain why this reaction is a redox reaction.
Answer
In this reaction, the oxidation number of chlorine changes. In NaClO2, chlorine has an oxidation state of +3, while in Cl2 it is 0 (elemental form). After the reaction, chlorine in ClO2 has an oxidation state of +4. Since there is an increase in oxidation number from +3 to +4 for chlorine, it indicates that chlorine is oxidized. Conversely, chlorine in Cl2 is reduced to +1 in ClO2F. Therefore, the reaction involves both oxidation and reduction processes, confirming it is a redox reaction.
Step 2
The central atom in the molecule of ClO2 is chlorine. Draw the 'dot-and-cross' diagram for ClO2. Show outer electrons only.
Answer
The 'dot-and-cross' diagram for ClO2 can be illustrated as follows.
- Chlorine (Cl) will be shown with 7 outer electrons (as dots) and each oxygen (O) will be represented with 6 outer electrons (as crosses).
- There will be a double bond between Cl and O, sharing two pairs of electrons.
The representation looks like this:
O: O:
||
Cl
• • • •
• • • •
Where the dots represent the outer electrons of chlorine and the crosses represent the outer electrons of oxygen.
Step 3
What is meant by the term order of reaction with respect to a particular reagent?
Answer
The order of reaction with respect to a particular reagent refers to the power to which the concentration of that reagent is raised in the rate law equation. It indicates how the rate of reaction changes with varying concentrations of that reagent. For example, if the rate of a reaction doubles when the concentration of a reactant is doubled, the order with respect to that reactant is 1.