Edexcel IAL Chemistry AS Decimal and Standard Form

Pearson Edexcel International Advanced Subsidiary/Advanced Level in Chemistry, Issue 1, September 2017Chemistry XCH11/YCH11

Practise Edexcel IAL Chemistry decimal and standard form skills by calculating reciprocal table values such as 1/t and recording small decimals to sensible precision.

How this is tested

Calculate reciprocal values such as 1/t in data tables and round small decimals to two significant figures.

[Maximum number: 1]

A student investigated the kinetics of the reaction between bromide ions, $\mathrm{Br}^{-}$ , and bromate(V) ions, $\mathrm{BrO}_{3}^{-}$ , in aqueous acid.

5 \mathrm{Br}^{-}(\mathrm{aq})+\mathrm{BrO}_{3}^{-}(\mathrm{aq})+6 \mathrm{H}^{+}(\mathrm{aq}) \rightarrow 3 \mathrm{Br}_{2}(\mathrm{aq})+3 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})

To determine the rate equation for the reaction, the student varied the concentration of bromide ions, bromate(V) ions and acid in turn.

The effect of the concentration of bromide ions was investigated first.

Procedure

Step 1 Add $10.0 \mathrm{~cm}^{3}$ of $0.0050 \mathrm{~mol} \mathrm{dm}^{-3}$ potassium bromate(V), $15.0 \mathrm{~cm}^{3}$ of acidified methyl orange indicator solution and $5.0 \mathrm{~cm}^{3}$ of $0.00010 \mathrm{~mol} \mathrm{dm}^{-3}$ aqueous phenol to a beaker labelled P.

Step 2 Prepare the contents of beaker Q for Run 1 as specified in the table.
Step 3 Pour the contents of beaker Q into beaker P and start a timer. Pour the contents of beaker P back into beaker Q and place beaker Q on a white tile.

Step 4 Stop the timer as soon as the mixture turns colourless. Record the time, along with the temperature of the solution.

Step 5 Repeat Steps 1 to 4 for the remaining runs.

Table for Question 3(c)(i) — Edexcel A-Level Chemistry AS

The student's results are shown.

Complete the table by calculating the remaining values of 1 / t.

How this is tested

Question 3(c)(i)