Acids, alkalis and titrations

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Question 26

The formula for hydrated iron(II) sulfate is $FeSO4⋅xH2O\text{FeSO}_4\cdot x\text{H}_2\text{O}$ .

The value of $x$ is a whole number between 1 and 10. It can be determined by carrying out a titration with $mol/dm30.0200\text{ mol/dm}^3$ potassium manganate(VII) ( $KMnO4\text{KMnO}_4$ ) solution as follows:

dissolve a sample of $FeSO4⋅xH2O\text{FeSO}_4\cdot x\text{H}_2\text{O}$ in water to make $cm3250\text{ cm}^3$ of solution
measure out $cm325.0\text{ cm}^3$ of this solution into a conical flask
add the $KMnO4\text{KMnO}_4$ solution using a burette until the end point is reached
record the volume of solution added
repeat the titration three more times

The table shows the results:

Titration number	1	2	3	4
Volume in $cm3\text{cm}^3$ of $KMnO4\text{KMnO}_4$ solution added	24.90	24.10	24.50	24.20
Concordant titration results ( $✓\checkmark$ )

Concordant results are those within $cm30.20\text{ cm}^3$ of each other. Identify the concordant results in the table.

[1]

Using the concordant results, calculate the average (mean) volume of $KMnO4\text{KMnO}_4$ solution added. Give your answer to 2 decimal places.

[2]

Which is the most suitable piece of apparatus to measure out $cm325.0\text{ cm}^3$ of $FeSO4\text{FeSO}_4$ solution?

A beaker
B gas syringe
C measuring cylinder
D pipette

[1]

These results were obtained in another titration:

parameter	value
mass of $FeSO4⋅xH2O\text{FeSO}_4\cdot x\text{H}_2\text{O}$ in $cm3250\text{ cm}^3$ of the $FeSO4\text{FeSO}_4$ solution	$g6.95\text{ g}$
average volume of $KMnO4\text{KMnO}_4$ solution added to $cm325.0\text{ cm}^3$ of solution	$cm325.00\text{ cm}^3$
concentration of the $KMnO4\text{KMnO}_4$ solution	$mol/dm30.0200\text{ mol/dm}^3$

Calculate the amount, in moles, of $KMnO4\text{KMnO}_4$ in $cm325.00\text{ cm}^3$ of solution.

[1]

In this reaction, one mole of $KMnO4\text{KMnO}_4$ reacts with five moles of $FeSO4\text{FeSO}_4$ . Calculate the amount, in moles, of $FeSO4\text{FeSO}_4$ in $cm325.0\text{ cm}^3$ of the $FeSO4\text{FeSO}_4$ solution.

[1]

Calculate the amount, in moles, of $FeSO4\text{FeSO}_4$ in $cm3250\text{ cm}^3$ of this $FeSO4\text{FeSO}_4$ solution.

[1]

Using your answer from (d)(iii), calculate the mass, in grams, of $FeSO4\text{FeSO}_4$ in the $g6.95\text{ g}$ of $FeSO4⋅xH2O\text{FeSO}_4\cdot x\text{H}_2\text{O}$ . [ $MrM_{\text{r}}$ of $FeSO4=152\text{FeSO}_4 = 152$ ]

[1]

In another experiment it is found that $g13.9\text{ g}$ of $FeSO4⋅xH2O\text{FeSO}_4\cdot x\text{H}_2\text{O}$ contains $g7.6\text{ g}$ of iron(II) sulfate ( $FeSO4\text{FeSO}_4$ ).

Calculate the mass of water in $g13.9\text{ g}$ of $FeSO4⋅xH2O\text{FeSO}_4\cdot x\text{H}_2\text{O}$ .

[1]

Calculate the amount, in moles, of $H2O\text{H}_2\text{O}$ in this mass of water.

[1]

Calculate the amount, in moles, of $FeSO4\text{FeSO}_4$ in $g7.6\text{ g}$ of iron(II) sulfate. [ $MrM_{\text{r}}$ of $FeSO4=152\text{FeSO}_4 = 152$ ]

[1]

Using your answers to parts (ii) and (iii), calculate the value of $x$ in $FeSO4⋅xH2O\text{FeSO}_4\cdot x\text{H}_2\text{O}$ .

[1]

Titration number

Volume in

cm3\text{cm}^3

KMnO4\text{KMnO}_4

solution added

24.90

24.10

24.50

24.20

Concordant titration results (

✓\checkmark

)

parameter

value

mass of

FeSO4⋅xH2O\text{FeSO}_4\cdot x\text{H}_2\text{O}

cm3250\text{ cm}^3

of the

FeSO4\text{FeSO}_4

solution

g6.95\text{ g}

average volume of

KMnO4\text{KMnO}_4

solution added to

cm325.0\text{ cm}^3

of solution

cm325.00\text{ cm}^3

concentration of the

KMnO4\text{KMnO}_4

solution

mol/dm30.0200\text{ mol/dm}^3

Acids, alkalis and titrations

Question 26

Acids, alkalis and titrations Questions

Acids, alkalis and titrations

Question 26

Acids, alkalis and titrations Questions