DP Chemistry Questionbank

5.0mol of Fe₂O₃(s) and 6.0mol of CO(g) react according to the equation below. What is the limiting reactant and how many moles of the excess reactant remain unreacted?

Fe₂O₃(s) + 3CO(g) → 2Fe(s) + 3CO₂(g)

5.00 g of an impure sample of hydrated ethanedioic acid, (COOH)₂•2H₂O, was dissolved in water to make 1.00 dm³ of solution. 25.0 cm³ samples of this solution were titrated against a 0.100 mol dm^-3 solution of sodium hydroxide using a suitable indicator.

(COOH)₂ (aq) + 2NaOH (aq) → (COONa)₂ (aq) + 2H₂O (l)

The mean value of the titre was 14.0 cm³.

(i) Suggest a suitable indicator for this titration. Use section 22 of the data booklet.

(ii) Calculate the amount, in mol, of NaOH in 14.0 cm³ of 0.100 mol dm^-3 solution.

(iii) Calculate the amount, in mol, of ethanedioic acid in each 25.0 cm³ sample.

(iv) Determine the percentage purity of the hydrated ethanedioic acid sample.

Determine the percentage experimental yield of the product after recrystallization. The molar masses are as follows: M(salicylic acid) = 138.13 g mol⁻¹, M(aspirin) = 180.17 g mol⁻¹. (You do not need to process the uncertainties in the calculation.)

The complete combustion of 15.0cm³ of a gaseous hydrocarbon X produces 60.0 cm³ of carbon dioxide gas and 75.0 cm³ of water vapour. What is the molecular formula of X? (All volumes are measured at the same temperature and pressure.) 

A. C₄H₆ 
B. C₄H₈ 
C. C₄H₁₀ 
D. C₆H₁₀ 

5.00 g of an impure sample of hydrated ethanedioic acid, (COOH)₂•2H₂O, was dissolved in water to make 1.00 dm³ of solution. 25.0 cm³ samples of this solution were titrated against a 0.100 mol dm^-3 solution of sodium hydroxide using a suitable indicator.

(COOH)₂ (aq) + 2NaOH (aq) → (COONa)₂ (aq) + 2H₂O (l)

The mean value of the titre was 14.0 cm³.

(i)   Calculate the amount, in mol, of NaOH in 14.0 cm³ of 0.100 mol dm^-3 solution.

(ii)  Calculate the amount, in mol, of ethanedioic acid in each 25.0 cm³ sample.

(iii) Determine the percentage purity of the hydrated ethanedioic acid sample.

The precipitate of sulfur makes the mixture cloudy, so a mark underneath the reaction mixture becomes invisible with time.

10.0 cm³ of 2.00 mol dm^-3 hydrochloric acid was added to a 50.0 cm³ solution of sodium thiosulfate at temperature, T1. Students measured the time taken for the mark to be no longer visible to the naked eye. The experiment was repeated at different concentrations of sodium thiosulfate.

Show that the hydrochloric acid added to the flask in experiment 1 is in excess.

Which volume, in cm³, of 0.20 mol dm^-3 NaOH (aq) is needed to neutralize 0.050 mol of H₂S(g)? 

H₂S(g) + 2NaOH(aq) → Na₂S(aq) + 2H₂O(l) 

A. 0.25 
B. 0.50 
C. 250 
D. 500

Suggest how the end point of the titration might be estimated from the graph.

Calculate the volume, in dm³, of nitrogen formed under SATP conditions. (The volume of 1 mol of gas = 24.8 dm³ at SATP.)

Calculate, showing your working, the mass of hydrazine needed to remove all the dissolved oxygen from 1000 dm³ of the sample.

State and explain how the graph would differ if 1 mol$$dm⁻³ sulfuric acid had been used instead of 1 mol$$dm⁻³ hydrochloric acid.

What is the expression for the volume of hydrogen gas, in dm³, produced at STP when 0.30 g of magnesium reacts with excess hydrochloric acid solution?

Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)

Molar volume of an ideal gas at STP = 22.7 dm³$$mol⁻¹

A.     $\frac{0.30\times 2\times 22.7}{24.31}$

B.     $\frac{0.30\times 22.7}{24.31}$

C.     $\frac{0.30\times 24.31}{22.7}$

D.     $\frac{0.30\times 22.7}{24.31\times 2}$

5.0 cm³ of 2.00 mol$$dm^–3 sodium carbonate solution, Na₂CO₃(aq), was added to a volumetric flask and the volume was made up to 500 cm³ with water. What is the concentration, in mol$$dm^–3, of the solution?

A.     0.0050

B.     0.0040

C.     0.020

D.     0.010

Which factors affect the molar volume of an ideal gas?

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

Calculate the amount, in mol, of NaOH(aq) used.

What is the maximum volume, in dm³, of CO₂(g) produced when 1.00 g of CaCO₃(s) reacts with 20.0 cm³ of 2.00 mol$$dm^–3 HCl(aq)?

CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g)

Molar volume of gas = 22.7 dm³$$mol^–1; M_r(CaCO₃) = 100.00

A.     $\frac{1}{2}\times \frac{20.0\times 2.0}{1000}\times 22.7$

B.     $\frac{20.0\times 2.0}{1000}\times 22.7$

C.     $\frac{1.0}{100.00}\times 22.7$

D.     $\frac{1.0}{100.00}\times 2\times 22.7$

Calculate the molar mass of the acid.

10.0 cm³ of the waste sample required 13.24 cm³ of the K₂Cr₂O₇ solution. Calculate the molar concentration of Sn²⁺(aq) in the waste sample.

The sample of K₂Cr₂O₇(s) in (i) was dissolved in distilled water to form 0.100 dm³ solution. Calculate its molar concentration.

Explain why this experiment might give a low result for the molar mass of butane.

Suggest one improvement to the investigation.

Calculate the amounts, in mol, of each reactant.

Calculate, in g, the theoretical yield of aspirin.

Which volume of ethane gas, in ${\mathrm{cm}}^3$, will produce $40 {\mathrm{cm}}^3$ of carbon dioxide gas when mixed with $140 {\mathrm{cm}}^3$ of oxygen gas, assuming the reaction goes to completion?

$2{\mathrm{C}}_2{\mathrm{H}}_6 \left(\mathrm{g}\right)+7{\mathrm{O}}_2 \left(\mathrm{g}\right)\to 4{\mathrm{CO}}_2 \left(\mathrm{g}\right)+6{\mathrm{H}}_2\mathrm{O} \left(\mathrm{g}\right)$

A.  $10$

B.  $20$

C.  $40$

D.  $80$

Calculate the volume of chlorine, in ${\mathrm{dm}}^3$, produced if the reaction is conducted at standard temperature and pressure (STP). Use section 2 of the data booklet.

Calculate the amount, in $\mathrm{mol}$, of manganese(IV) oxide added.

Determine the limiting reactant, showing your calculations.

Determine the excess amount, in $\mathrm{mol}$, of the other reactant.

Determine the excess amount, in $\mathrm{mol}$, of the other reactant.

Determine the limiting reactant, showing your calculations.

Calculate the amount, in $\mathrm{mol}$, of manganese(IV) oxide added.

Calculate the volume of chlorine, in ${\mathrm{dm}}^3$, produced if the reaction is conducted at standard temperature and pressure (STP). Use section 2 of the data booklet.

Show that the mass of the ${}_{238}\mathrm{U}$ isotope in the rock is $0.639 \mathrm{kg}$.

Suggest a wavenumber absorbed by methane gas.

Suggest a wavenumber absorbed by methane gas.

Show that the mass of the ²³⁸U isotope in the rock is $0.639 \mathrm{kg}$.

The vapour pressure of pure ethanal at $20°\mathrm{C}$ is $101 \mathrm{kPa}$.

Calculate the vapour pressure of ethanal above the liquid mixture at $20°\mathrm{C}$.

Calculate the mole fraction of ethanal in the mixture.

Determine the volume, in dm³, of 0.015 mol dm⁻³ calcium hydroxide solution needed to neutralize 35.0 cm³ of 0.025 mol dm⁻³ HCl (aq).

What is the pressure, in Pa, inside a 1.0 m³ cylinder containing 10 kg of H₂ (g) at 25 ºC?

R = 8.31 J K^–1 mol^–1; pV = nRT

A. $\frac{1\times {10}^4\times 8.31\times 25}{1.0\times {10}^3}$

B. $\frac{5\times {10}^2\times 8.31\times 298}{1.0}$

C. $\frac{1\times 8.31\times 25}{1.0\times {10}^3}$

D. $\frac{5\times {10}^3\times 8.31\times 298}{1.0}$

0.150 g sample of menthol, when vaporized, had a volume of 0.0337 dm³ at 150 °C and 100.2 kPa. Calculate its molar mass showing your working.

Calculate the concentration of ethanoic acid, CH₃COOH, in mol dm^–3.

0.150 g sample of menthol, when vaporized, had a volume of 0.0337 dm³ at 150 °C and 100.2 kPa. Calculate its molar mass showing your working.

What volume of oxygen, in dm³ at STP, is needed when 5.8 g of butane undergoes complete combustion?

$2{\mathrm{C}}_4{\mathrm{H}}_{10} \left(\mathrm{g}\right)+13{\mathrm{O}}_2 \left(\mathrm{g}\right)\to 8{\mathrm{CO}}_2 \left(\mathrm{g}\right)+10{\mathrm{H}}_2\mathrm{O} \left(\mathrm{l}\right)$

A.  $2\times \frac{5.8}{12.01\times 4+1.01\times 10}\times 13\times 22.7$

B.  $\frac{5.8}{12.01\times 4+1.01\times 10}\times \frac{13}{2}\times 22.7$

C.  $\frac{5.8}{12.01\times 4+1.01\times 10}\times \frac{2}{13}\times 22.7$

D.  $\frac{5.8}{12.01\times 4+1.01\times 10}\times \frac{13}{2}\times \frac{22.7}{1000}$

0.20 mol of magnesium is mixed with 0.10 mol of hydrochloric acid.

$\text{Mg\hspace{0.05em}(s)}+\text{2HCl} \text{(aq)}\to {\text{MgCl}}_{\text{2}} \text{(aq)}+{\text{H}}_{\text{2}} \text{(g)}$

Which is correct?

8.00 g of methane is completely converted to methanol. Calculate, to three significant figures, the final volume of hydrogen at STP, in dm³. Use sections 2 and 6 of the data booklet.

A gaseous sample of nitrogen, contaminated only with hydrogen sulfide, was reacted with excess sodium hydroxide solution at constant temperature. The volume of the gas changed from 550 cm³ to 525 cm³.

Determine the mole percentage of hydrogen sulfide in the sample, stating one assumption you made.

8.00 g of methane is completely converted to methanol. Calculate, to three significant figures, the final volume of hydrogen at STP, in dm³. Use sections 2 and 6 of the data booklet.

Calcium carbonate is heated to produce calcium oxide, CaO.

CaCO₃(s) → CaO (s) + CO₂(g)

Calculate the volume of carbon dioxide produced at STP when 555 g of calcium carbonate decomposes. Use sections 2 and 6 of the data booklet.

Determine the volume, in dm³, of 0.015 mol dm⁻³ calcium hydroxide solution needed to neutralize 35.0 cm³ of 0.025 mol dm⁻³ HCl (aq).

Determine the mass, in g, of CaCO₃(s) produced by reacting 2.41 dm³ of 2.33 × 10⁻² mol dm⁻³ of Ca(OH)₂ (aq) with 0.750 dm³ of CO₂ (g) at STP.

2.85 g of CaCO₃ was collected in the experiment in e(i). Calculate the percentage yield of CaCO₃.

(If you did not obtain an answer to e(i), use 4.00 g, but this is not the correct value.)

Calcium carbonate is heated to produce calcium oxide, CaO.

CaCO₃(s) → CaO (s) + CO₂(g)

Calculate the volume of carbon dioxide produced at STP when 555 g of calcium carbonate decomposes. Use sections 2 and 6 of the data booklet.

Determine the mass, in g, of CaCO₃(s) produced by reacting 2.41 dm³ of 2.33 × 10⁻² mol dm⁻³ of Ca(OH)₂ (aq) with 0.750 dm³ of CO₂ (g) at STP.

2.85 g of CaCO₃ was collected in the experiment in d(i). Calculate the percentage yield of CaCO₃.

(If you did not obtain an answer to d(i), use 4.00 g, but this is not the correct value.)

Calculate the maximum volume of CO₂, in cm³, produced at STP by the combustion of 0.600 g of urea, using sections 2 and 6 of the data booklet.

Urea can be made by reacting potassium cyanate, KNCO, with ammonium chloride, NH₄Cl.

KNCO(aq) + NH₄Cl(aq) → (H₂N)₂CO(aq) + KCl(aq)

Determine the maximum mass of urea that could be formed from 50.0 cm³ of 0.100 mol dm⁻³ potassium cyanate solution.

What is the percentage yield when 7 g of ethene produces 6 g of ethanol?

M_r(ethene) = 28 and M_r(ethanol) = 46

C₂H₄(g) + H₂O(g) → C₂H₅OH(g)

A.     $\frac{6\times 7\times 100}{28\times 46}$

B.     $\frac{6\times 46\times 100}{7\times 28}$

C.     $\frac{6\times 28}{7\times 46\times 100}$

D.     $\frac{6\times 28\times 100}{7\times 46}$

Urea can be made by reacting potassium cyanate, KNCO, with ammonium chloride, NH₄Cl.

                                      KNCO(aq) + NH₄Cl(aq) → (H₂N)₂CO(aq) + KCl(aq)

Determine the maximum mass of urea that could be formed from 50.0 cm³ of 0.100 mol dm⁻³ potassium cyanate solution.

What is the volume, in cm³, of the final solution if 100 cm³ of a solution containing 1.42 g of sodium sulfate, Na₂SO₄, is diluted to the concentration of 0.020 mol dm^–3?

M_r(Na₂SO₄) = 142

A.     50

B.     400

C.     500

D.     600

What is the percentage yield when 2.0 g of ethene, C₂H₄, is formed from 5.0 g of ethanol, C₂H₅OH?
M_r(ethene) = 28; M_r(ethanol) = 46

A.     $\frac{2.0}{28}\times \frac{5.0}{46}\times 100$

B.     $\frac{\frac{2.0}{28}}{\frac{5.0}{46}}\times 100$

C.     $\frac{28}{2.0}\times \frac{5.0}{46}\times 100$

D.     $\frac{\frac{28}{2.0}}{\frac{5.0}{46}}\times 100$

Calculate the amount, in mol, of H₂SO₄.

The excess sulfuric acid required 20.80 cm³ of 0.1133 mol dm⁻³ NaOH for neutralization.

Calculate the amount of excess acid present.

Calculate the amount of H₂SO₄ that reacted with Mg(OH)₂.

Calculate the percentage by mass of magnesium hydroxide in the 1.24 g antacid tablet to three significant figures.

Calculate the amount, in moles of Na₂S₂O₃ used in the titration.

Calculate the concentration of dissolved oxygen, in mol dm⁻³, in the sample.

Calculate the concentration of H₃PO₄ if 25.00 cm³ is completely neutralised by the addition of 28.40 cm³ of 0.5000 mol dm⁻³ NaOH.

Calculate the concentration of H₃PO₄ if 25.00 cm³ is completely neutralised by the addition of 28.40 cm³ of 0.5000 mol dm⁻³ NaOH.

Calculate the amount, in moles of Na₂S₂O₃ used in the titration.

Calculate the concentration of dissolved oxygen, in mol dm⁻³, in the sample.

Which sample contains the fewest moles of HCl?

N_A = 6.02 × 10²³mol^–1.

Molar volume of an ideal gas at STP = 22.7 dm³mol^–1.

A.  10.0 cm³ of 0.1 mol dm^–3 HCl (aq)

B.  6.02 × 10²⁴ molecules of HCl (g)

C.  0.365 g of HCl (g)

D.  2.27 dm³ of HCl (g) at STP

The mass of copper obtained experimentally was 0.872 g. Calculate the percentage yield of copper.

Suggest why the end point of the titration is difficult to determine, even with the addition of starch to turn the remaining free iodine black.

Determine the limiting reactant showing your working.

Outline how a solution of 0.0100 mol dm⁻³ is obtained from a standard 1.000 mol dm⁻³ copper(II) sulfate solution, including two essential pieces of glassware you would need.

Determine the limiting reactant showing your working.

An antacid tablet containing 0.50 g of NaHCO₃ (M_r = 84) is dissolved in water to give a volume of 250 cm³. What is the concentration, in mol dm⁻³, of HCO₃⁻ in this solution?

A.   $\frac{0.250\times 84}{0.50}$

B.   $\frac{0.50}{84\times 0.250}$

C.   $\frac{250\times 84}{0.50}$

D.   $\frac{0.50}{84\times 250}$

The mass of copper obtained experimentally was 0.872 g. Calculate the percentage yield of copper.

Titration is another method for analysing the solution obtained from adding brass to nitric acid.

Copper(II) ions are reduced to copper(I) iodide by the addition of potassium iodide solution, releasing iodine that can be titrated with sodium thiosulfate solution, Na₂S₂O₃ (aq). Copper(I) iodide is a white solid.

4I⁻ (aq) + 2Cu²⁺ (aq) → 2CuI (s) + I₂ (aq)

I₂ (aq) + 2S₂O₃²⁻ (aq) → 2I⁻ (aq) + S₄O₆²⁻ (aq)

Suggest why the end point of the titration is difficult to determine, even with the addition of starch to turn the remaining free iodine black.

Copper(II) ions are reduced to copper(I) iodide by the addition of potassium iodide solution, releasing iodine that can be titrated with sodium thiosulfate solution, Na₂S₂O₃ (aq). Copper(I) iodide is a white solid.

4I⁻ (aq) + 2Cu²⁺ (aq) → 2CuI (s) + I₂ (aq)

I₂ (aq) + 2S₂O₃²⁻ (aq) → 2I⁻ (aq) + S₄O₆²⁻ (aq)

Deduce the overall equation for the two reactions by combining the two equations.

Outline how a solution of 0.0100 mol dm⁻³ is obtained from a standard 1.000 mol dm⁻³ copper(II) sulfate solution, including two essential pieces of glassware you would need.

Assume the reaction in (a)(i) is the only one occurring and it goes to completion, but some product has been lost from the crucible. Deduce the percentage yield of magnesium oxide in the crucible.

Evaluate whether this, rather than the loss of product, could explain the yield found in (b)(iii).

Determine the concentration, in mol dm^–3, of the solution formed when 900.0 dm³ of NH₃(g) at 300.0 K and 100.0 kPa, is dissolved in water to form 2.00 dm³ of solution. Use sections 1 and 2 of the data booklet.

Assume the reaction in (a)(i) is the only one occurring and it goes to completion, but some product has been lost from the crucible. Deduce the percentage yield of magnesium oxide in the crucible.

Evaluate whether this, rather than the loss of product, could explain the yield found in (b)(iii).

Determine the concentration, in mol dm^–3, of the solution formed when 900.0 dm³ of NH₃(g) at 300.0 K and 100.0 kPa, is dissolved in water to form 2.00 dm³ of solution. Use sections 1 and 2 of the data booklet.

Calculate the molar concentration of the resulting solution of lithium hydroxide.

Calculate the volume of hydrogen gas produced, in cm³, if the temperature was 22.5 °C and the pressure was 103 kPa. Use sections 1 and 2 of the data booklet.

Sodium peroxide, Na₂O₂, is formed by the reaction of sodium oxide with oxygen.

2Na₂O (s) + O₂ (g) → 2Na₂O₂ (s)

Calculate the percentage yield of sodium peroxide if 5.00g of sodium oxide produces 5.50g of sodium peroxide.

Outline why a real gas differs from ideal behaviour at low temperature and high pressure.

Explain why, as the reaction proceeds, the pressure increases by the amount shown.

The experiment is repeated using the same amount of dinitrogen monoxide in the same apparatus, but at a lower temperature.

Sketch, on the axes in question 2, the graph that you would expect.

100.0cm³ of soda water contains 3.0 × 10⁻²g NaHCO₃.

Calculate the concentration of NaHCO₃ in mol dm⁻³.

A mean daily lead intake of greater than 5.0 × 10⁻⁶ g per kg of body weight results in increased lead levels in the body.

Calculate the volume, in dm³, of tap water from experiment 8 which would exceed this daily lead intake for an 80.0 kg man.

What volume of carbon dioxide, CO₂ (g), can be obtained by reacting 1 dm³ of methane, CH₄ (g), with 1 dm³ of oxygen, O₂ (g)?

CH₄ (g) + 2O₂ (g) → CO₂ (g) + 2H₂O (l)

A. 0.5 dm³

B. 1 dm³

C. 2 dm³

D. 6 dm³

Sodium peroxide, Na₂O₂, is formed by the reaction of sodium oxide with oxygen.

2Na₂O (s) + O₂ (g) → 2Na₂O₂ (s)

Calculate the percentage yield of sodium peroxide if 5.00 g of sodium oxide produces 5.50 g of sodium peroxide.

Explain why, as the reaction proceeds, the pressure increases by the amount shown.

100.0 cm³ of soda water contains 3.0 × 10⁻² g NaHCO₃.

Calculate the concentration of NaHCO₃ in mol dm⁻³.

The experiment is repeated using the same amount of dinitrogen monoxide in the same apparatus, but at a lower temperature.

Sketch, on the axes in question 2, the graph that you would expect.

A mean daily lead intake of greater than 5.0 × 10⁻⁶ g per kg of body weight results in increased lead levels in the body.

Calculate the volume, in dm³, of tap water from experiment 8 which would exceed this daily lead intake for an 80.0 kg man.

Which graph would not show a linear relationship for a fixed mass of an ideal gas with all other variables constant?

A. P against V

B. P against $\frac{1}{\text{V}}$

C. P against T

D. V against T

What is the concentration, in mol dm⁻³, of 20.0 g of NaOH (M_r = 40.0) in 500.0 cm³?

A. 0.250

B. 0.500

C. 1.00

D. 4.00

What is the volume of gas when the pressure on 100 cm³ of gas is changed from 400 kPa to 200 kPa at constant temperature?

A. 50.0 cm³

B. 100 cm³

C. 200 cm³

D. 800 cm³

Calculate the pressure, in kPa, of this gas in a 10.0 dm³ air bag at 127°C, assuming no gas escapes.

0.10 mol of hydrochloric acid is mixed with 0.10 mol of calcium carbonate.

2HCl (aq) + CaCO₃ (s) → CaCl₂ (aq) + H₂O (l) + CO₂ (g)

Which is correct?

The day 5 sample contained 5.03 × 10⁻⁵ moles of oxygen.

Determine the 5-day biochemical oxygen demand of the pond, in mg dm⁻³ (“parts per million”, ppm).

Solid copper(II) chloride absorbs moisture from the atmosphere to form a hydrate of formula CuCl₂•$x$H₂O.

A student heated a sample of hydrated copper(II) chloride, in order to determine the value of $x$. The following results were obtained:

Mass of crucible = 16.221 g
Initial mass of crucible and hydrated copper(II) chloride = 18.360 g
Final mass of crucible and anhydrous copper(II) chloride = 17.917 g

Determine the value of $x$.

Calculate the pH of a buffer solution which contains 0.20 mol dm⁻³ ethanoic acid and 0.50 mol dm⁻³ sodium ethanoate. Use section 1 of the data booklet.

pK_a (ethanoic acid) = 4.76

1.40 × 10⁻³ g of NaOH (s) are dissolved in 250.0 cm³ of 1.00 × 10⁻¹¹ mol dm⁻³ Pb(OH)₂ (aq) solution.

Determine the change in lead ion concentration in the solution, using section 32 of the data booklet.

Solid copper(II) chloride absorbs moisture from the atmosphere to form a hydrate of formula CuCl₂•$x$H₂O.

A student heated a sample of hydrated copper(II) chloride, in order to determine the value of $x$. The following results were obtained:

Mass of crucible = 16.221 g
Initial mass of crucible and hydrated copper(II) chloride = 18.360 g
Final mass of crucible and anhydrous copper(II) chloride = 17.917 g

Determine the value of $x$.