Edexcel IAL Chemistry AS Topic 1 Formulae, equations and moles

Pearson Edexcel IAL Chemistry syllabusChemistry YCH11First assessment 2019

Write the chemical relationship first, convert every quantity to moles with consistent units and use formula or equation ratios before reporting the requested value.

Exam points

Calculate moles, particles, masses or gas volumes using molar quantities and constants.
Write balanced full or ionic equations with correct formulae, charges and state symbols.
Apply ppm, concentration or composition data to determine a chemical amount or formula.

[Maximum number: 2]

The maximum permitted concentration of sulfur in diesel fuel is 10 mg of sulfur in 1 kg of diesel fuel.

(a)

What is this concentration of sulfur in ppm?

0.00001

0.01

10000

[ 1 ]

(b)

3.2 kg of this diesel fuel is burned in air.

What is the maximum volume, in $\mathrm{dm}^{3}$ , of sulfur dioxide which can be produced, measured at room temperature and pressure (r.t.p.)?
[Molar volume of a gas at r.t.p. $=24 \mathrm{dm}^{3} \mathrm{~mol}^{-1}$ ]

0.024

0.77

2.4

[ 1 ]

[Maximum number: 4]

A mass of 0.23 g of sodium was added to $350 \mathrm{~cm}^{3}$ water to form hydrogen and a solution of sodium hydroxide.

\mathrm{Na}(\mathrm{~s})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{NaOH}(\mathrm{aq})+1 / 2 \mathrm{H}_{2}(\mathrm{~g})

(a)

What is the concentration, in $\mathrm{mol} \mathrm{dm}^{-3}$ , of sodium hydroxide in the solution formed?

0.010

0.029

0.29

0.66

[ 1 ]

(b)

What is the maximum volume, in $\mathrm{cm}^{3}$ , of hydrogen which could be formed, measured at r.t.p.?
[Molar volume of a gas at r.t.p. $=24 \mathrm{dm}^{3} \mathrm{~mol}^{-1}$ ]

120

240

480

2800

[ 1 ]

(c)

The sodium hydroxide solution was neutralised with sulfuric acid.

Which is the ionic equation for this reaction?
□

A $\mathrm{H}^{+}(\mathrm{aq})+\mathrm{OH}^{-}(\mathrm{aq}) \rightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{l})$

□

B $\mathrm{SO}_{4}^{2-}(\mathrm{aq})+2 \mathrm{Na}^{+}(\mathrm{aq}) \rightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}(\mathrm{aq})$

□

C $\mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq})+2 \mathrm{Na}^{+}(\mathrm{aq})+2 \mathrm{OH}^{-}(\mathrm{aq}) \rightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})$

□

D $2 \mathrm{H}^{+}(\mathrm{aq})+\mathrm{SO}_{4}^{2-}(\mathrm{aq})+2 \mathrm{Na}^{+}(\mathrm{aq})+2 \mathrm{OH}^{-}(\mathrm{aq}) \rightarrow 2 \mathrm{Na}^{+}(\mathrm{aq})+\mathrm{SO}_{4}^{2-}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})$

[ 1 ]

(d)

Sodium hydroxide solution was added to magnesium sulfate solution.

The equation for the reaction is shown.

2 \mathrm{NaOH}(\mathrm{aq})+\mathrm{MgSO}_{4}(\mathrm{aq}) \rightarrow \mathrm{Mg}(\mathrm{OH})_{2}(\mathrm{~s})+\mathrm{Na}_{2} \mathrm{SO}_{4}(\mathrm{aq})

What is the atom economy (by mass) for the production of magnesium hydroxide?
$\left[\begin{array}{llll}A_{\mathrm{r}} \text { values: } & \mathrm{H}=1.0 & \mathrm{O}=16.0 & \mathrm{Na}=23.0\end{array} \mathrm{Mg}=24.3 \quad \mathrm{~S}=32.1\right]$

29.1%

41.0\%

48.4%

50.0\%

[ 1 ]

[Maximum number: 2]

Ammonium iron(II) sulfate, $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{Fe}\left(\mathrm{SO}_{4}\right)_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}$ , is a double salt that is used as a source of iron(II) ions.

(a)

What is the relative formula mass of the double salt?

277.9

284.0

392.0

447.8

[ 1 ]

(b)

What is the total number of ions present in 0.1 mol of the double salt?
[Avogadro constant $(L)=6.02 \times 10^{23} \mathrm{~mol}^{-1}$ ]
□ A $1.80 \times 10^{23}$
□ B $\quad 2.41 \times 10^{23}$
□ C $3.01 \times 10^{23}$
□ D $\quad 6.62 \times 10^{23}$

\left[\begin{array}{llll} A_{r} \text { values: } & \mathrm{H}=1.0 & \mathrm{~N}=14.0 & \mathrm{O}=16.0 \end{array} \mathrm{~S}=32.1 \quad \mathrm{Fe}=55.8\right]

B 284.0
C 392.0
D 447.8

[ 1 ]

[Maximum number: 1]

What is the minimum volume of oxygen gas, measured at room temperature and pressure, required for the complete combustion of 9.2 g of $\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}_{3}\left(M_{\mathrm{r}}=92\right)$ ?
[Molar volume of gas at room temperature and pressure $=24.0 \mathrm{dm}^{3} \mathrm{~mol}^{-1}$ ]

$4.8 \mathrm{dm}^{3}$

$8.4 \mathrm{dm}^{3}$

$12.0 \mathrm{dm}^{3}$

$16.8 \mathrm{dm}^{3}$

[Maximum number: 7]

This question is about the investigation of an organic compound X. X is a liquid at room temperature and pressure, which turns damp red litmus paper blue.

(a)

When 0.493 g of X was vaporised, $157 \mathrm{~cm}^{3}$ of dry air was displaced, measured at $15^{\circ} \mathrm{C}$ and 103000 Pa.

Calculate the molar mass of X, using the ideal gas equation.
You must show your working.

[ 4 ]

(b)

X reacted vigorously with ethanoyl chloride forming steamy fumes and a white solid Y.

[ 3 ]

(i)

Analysis of Y showed that its composition by mass was 62.6% carbon; 11.3 \% hydrogen; 12.2 \% nitrogen; 13.9\% oxygen.

Determine the empirical formula of Y. You must show your working.

[ 3 ]

[Maximum number: 2]

This question is about an ester, Y, with the molecular formula $\mathrm{C}_{8} \mathrm{H}_{16} \mathrm{O}_{2}$ .

Y contains 66.7% carbon, 11.1% hydrogen and 22.2% oxygen by mass. Show that these data are consistent with its molecular formula.

[Maximum number: 9]

Potassium chlorate(V), KClO3, is a crystalline solid used in fireworks.
It is produced by the Liebig Process in two stages.
Stage 1 Chlorine gas is passed through hot calcium hydroxide solution forming calcium chlorate(V), $\mathrm{Ca}\left(\mathrm{ClO}_{3}\right)_{2}$ .

6 \mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{aq})+6 \mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow \mathrm{Ca}\left(\mathrm{ClO}_{3}\right)_{2}(\mathrm{aq})+5 \mathrm{CaCl}_{2}(\mathrm{aq})+6 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})

Stage 2 Potassium chloride solution is then added to form potassium chlorate(V).

\mathrm{Ca}\left(\mathrm{ClO}_{3}\right)_{2}(\mathrm{aq})+2 \mathrm{KCl}(\mathrm{aq}) \rightarrow 2 \mathrm{KClO}_{3}(\mathrm{aq})+\mathrm{CaCl}_{2}(\mathrm{aq})

The solution is heated to reduce its volume and then allowed to crystallise.
The crystals are filtered off.
The remaining filtrate is evaporated further to obtain more crystals.

(a)

Write the overall equation for the Liebig Process.

State symbols are not required.

[ 1 ]

(b)

Calculate the overall atom economy by mass for the production of potassium chlorate(V), $\mathrm{KClO}_{3}$ , using your equation in (a)(i).

[ 3 ]

(c)

The crystals of potassium chlorate(V) formed also contain some halide ion impurities.

[ 5 ]

(i)

1.52 g of impure potassium chlorate(V), formed in the Liebig Process, was heated until the mass of solid remaining was constant at 1.02 g .

The reaction that occurred was

2 \mathrm{KClO}_{3}(\mathrm{~s}) \rightarrow 2 \mathrm{KCl}(\mathrm{~s})+3 \mathrm{O}_{2}(\mathrm{~g})

The impurities present did not decompose on heating.
Calculate the percentage purity of the sample.
Give your answer to an appropriate number of significant figures.

[ 5 ]

Exam points

Question 1

Question 1(a)

Question 1(b)

Question 4

Question 4(a)

Question 4(b)

Question 4(c)

Question 4(d)

Question 7

Question 7(a)

Question 7(c)

Question 17

Question 19

Question 19(a)(ii)

Question 19(b)

Question 19(b)(iii)

Question 17(a)

Question 22

Question 22(a)(i)

Question 22(a)(ii)

Question 22(c)

Question 22(c)(ii)