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QLDChemistryQuick questions

Unit 3: Equilibrium, acids and redox reactions

Quick questions on Oxidation numbers and half-equations (QCE Chemistry Unit 3)

5short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What are constructing half-equations?
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A half-equation shows either the oxidation or the reduction half of a redox reaction. The protocol for aqueous solution:
What is half-equations in basic solution?
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When QCAA states the reaction occurs in basic conditions, do the acidic-conditions protocol first, then add OH- to both sides to neutralise the H+, and simplify the resulting H2O on each side.
What is q1?
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Assign oxidation numbers to all elements in (a) KMnO4\text{KMnO}_4, (b) Cr2O72βˆ’\text{Cr}_2 \text{O}_7^{2-}, (c) H2O2\text{H}_2 \text{O}_2. [3 marks]
What is q2?
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Balance the half-equation NO3βˆ’β†’NO\text{NO}_3^- \rightarrow \text{NO} in acidic solution. [3 marks]
What is q3?
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Combine half-equations for MnO4βˆ’\text{MnO}_4^-/Mn2+^{2+} and C2O42βˆ’\text{C}_2 \text{O}_4^{2-}/CO2\text{CO}_2 in acid. (a) Write both. (b) Combine into a balanced overall equation.

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