Astudent is asked to balance an equation by using the half-reaction method. he determines the two half reactions as shown below. 2 upper b r superscript minus right arrow upper b r subscript 2 plus 2 e superscript minus. second line: upper c l subscript 2 plus 2 e superscript minus right arrow 2 upper c l superscript minus. what should he write as the final, balanced equation? upper c l subscript 2 plus 2 upper b r superscript minus right arrow upper b r subscript 2 plus 2 upper c l superscript minus. upper c l subscript 2 plus 2 upper b r superscript minus, plus 2 e superscript minus right arrow upper b r subscript 2 plus 2 upper c l superscript minus. upper c l subscript 2 plus 2 upper b r superscript minus right arrow upper b r subscript 2 plus 2 upper c l superscript minus, plus 2 e superscript minus. upper c l subscript 2 plus upper b r superscript minus plus 2 e superscript minus right arrow upper b r subscript 2 plus upper c l superscript minus, plus 2 e superscript minus.

Complete Question:

                                  A student is asked to balance an equation by using the half-reaction method. He determines the two half reactions as shown below.

2 Br⁻ → Br₂ + 2e⁻

Cl₂ + 2e⁻ → 2Cl⁻

What should he write as the final, balances equation ?

Cl₂ + 2Br⁻ → Br₂ + 2 Cl⁻

Cl₂ + 2 Br⁻ + 2 e- → Br₂ + 2 Cl⁻

Cl₂ + 2 Br⁻ → Br₂ + Cl⁻ + 2 e⁻

Cl₂ + Br⁻ + 2e- → Br₂ + Cl⁻ + 2e⁻

                   Cl₂ + 2Br⁻ → Br₂ + 2 Cl⁻ is the correct answer.

Explanation:

                     First half equation is as

                                        2 Br⁻ → Br₂ + 2e⁻

This is oxidation reaction in which two bromide ions each containing one extra electron combine to form bromine molecule with the removal of two electrons. This removal of electrons is called as oxidation.

                     Second half equation is as

                                         Cl₂ + 2e⁻ → 2Cl⁻

This is reduction reaction in which one molecule of chlorine gains two electrons and split apart to form two chloride ions. This gain of electrons is called as reduction.

Hence, in overall reaction the two electrons lost by bromine will be gained by the chlorine molecule forming a bromine molecule and a chloride ions. i.e.

                                      Cl₂ + 2Br⁻ → Br₂ + 2 Cl⁻

Explanation:

C)

1. they vary with a higher number because boiling is way hotter than melting

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.