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CHEMISTRY, M6 2015 VCE 23 MC

The following table shows the value of the ionisation constant of pure water at various temperatures and at a constant pressure.

Given this data, which one of the following statements about pure water is correct?

  1. The  will decrease with increasing temperature.
  2. The  will increase with increasing temperature.
  3. Its pH will increase with increasing temperature.
  4. Its pH will always be exactly 7 at any temperature.
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Show Worked Solution

→ Table shows that increases as temperature increases.

→ Ionisation equation shifts right as temperature increases, causing an increase in and (eliminate A).

→ pH decreases as and temperature increase (eliminate C).

→ pH of water = 7 at 25°C only (eliminate D).

♦ Mean mark 55%.

CHEMISTRY, M6 EQ-Bank 3 MC

The structure of an organic compound is shown.
 

Which row of the table correctly shows how this compound reacts with bromine water and with blue litmus?
 

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→ Organic compound is sorbic acid.

→ Bromine water changes from a bright yellow to a colourless solution when it reacts with sorbic acid.

→ The acidic nature of the organic compound will turn blue litmus red.