Redox

Hydrogen peroxide, H₂O₂, reacts with an oxide M₂O according to the following reaction:

M₂O (s) + H₂O₂ (aq) --> 2M(s) + H₂O (l) + O₂(g)

• M₂O is acting as oxidising agent

• M₂O is acting as catalyst

• H₂O₂ is acting as oxidising agent

• H₂O₂ is reduced to H₂O₂ by the removal of oxygen.

Answer explanation

count the oxidation states!

In which of the following conversions does the oxidation state of nitrogen show the largest increase?

• Ammonia to nitrogen gas

• ammonia to ammonium ion

• Nitrogen dioxide to nitric acid

• nitrogen monoxide to nitrogen dioxide

Answer explanation

be mindful of the overall charge in nitrate ion when calculating the oxidation state of nitrogen.

When potassium manganate (VII) is added to substance X, the solution changes from purple to colourless. What is X?

• oxidising agen

• reducing agent

Answer explanation

what is the color of potassium manganate(VII) and what does it do?

See TB page 212

Colorless potassium iodide is added to colourless solution Y. The solution turns brown.

Which of the following best describe the reaction?

• Potassium iodide oxidises Y to brown color

• Potassium iodide reduces Y to brown color

• Y oxidises potassium iodide to brown Iodine solution

• Y reduces potassium iodide to brown solution

Answer explanation

see TB page 211

Which of the following underline substance has the highest oxidation state?

• NO₂

• SO₃

• KMnO₄

• KClO₃

Answer explanation

highest = most positive

X₂O (s) + H₂O₂ (aq) --> 2X(s) + H₂O (l) + O₂(g)

Which substance is the reducing agent?

• X₂O

• H₂O₂

• X

• H₂O

Answer explanation

reducing agents undergo _____ ?

2Fe (s) + 2KMnO₄ (aq) → Fe₂O₃ (s) + 2MnO₂ (s) + K₂O (aq)

which substance is the oxidising agent?

• Fe

• KMnO₄

• Fe₂O₃

• K₂O