DP Chemistry Questionbank

CT values are influenced by temperature and by pH. The table below shows the CT values for chlorine needed to achieve 99% inactivation of a specific bacterium at stated values of pH and temperature.

(i) With reference to the temperature data in the table, suggest why it may be more difficult to treat water effectively with chlorine in cold climates.

(ii) Sketch a graph on the axes below to show how the CT value (at any temperature) varies with pH.

(iii) Comment on the relative CT values at pH 6.0 and pH 9.0 at each temperature.

(iv) Chlorine reacts with water as follows:

Cl₂ (g) + H₂O (l) $\rightleftharpoons$ HOCl (aq) + HCl (aq)

HOCl (aq) $\rightleftharpoons$ OCl⁻ (aq) + H⁺ (aq)

Predict how the concentrations of each of the species HOCl (aq) and OCl⁻ (aq) will change if the pH of the disinfected water increases.

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

Calculate the percentage uncertainty of the volume of the aqueous sodium hydroxide.

A student produced these results with [H⁺] = 0.15 mol$$dm⁻³. Propanone and acid were in excess and iodine was the limiting reagent.

Determine the relative rate of reaction when [H⁺] = 0.15 mol$$dm⁻³.

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.

Dose response curves are determined for each drug.

Outline the significance of range “a”.

Outline the effect of decreasing pH on the oxygen saturation of hemoglobin.

Explain the shape of the curve at low oxygen partial pressure up to about 5 kPa.

Sketch a graph on the axes above to show the effect of decreasing pH on the binding of oxygen to hemoglobin (the Bohr Effect).

The following graph represents world energy consumption by type for the years 1988–2013.

Estimate the percentage of energy consumption which did not directly produce CO₂ in 2013.

Deduce the relationship between the concentration of N₂O₅ and the rate of reaction.

Predict from your line of best fit the rate of reaction when the concentration of HCl is 1.00 mol dm⁻³.

Draw the best fit line for the reaction excluding point D.

The graph shows Gibbs free energy of a mixture of N₂O₄(g) and NO₂(g) in different proportions.

N₂O₄(g) $\rightleftharpoons$ 2NO₂(g)

Which point shows the system at equilibrium?

Deduce the equation for the relationship between absorbance and concentration.

Sketch the pH curve for the titration of 25.0 cm³ of ethylamine aqueous solution with 50.0 cm³ of butanoic acid aqueous solution of equal concentration. No calculations are required.

Sketch a graph of the concentration of iron(II) sulfate, FeSO₄, against time as the reaction proceeds.

The original piece of brass weighed 0.200 g. The absorbance was 0.32.

Calculate, showing your working, the percentage of copper by mass in the brass.

Outline how the initial rate of reaction can be determined from the graph in part (c)(i).

The original piece of brass weighed 0.200 g. The absorbance was 0.32.

Calculate, showing your working, the percentage of copper by mass in the brass.

Sketch a graph of the concentration of iron(II) sulfate, FeSO₄, against time as the reaction proceeds.

Outline how the initial rate of reaction can be determined from the graph in part (c)(i).

Deduce the equation for the relationship between absorbance and concentration.

20 cm³ of 1 mol dm⁻³ sulfuric acid was added dropwise to 20 cm³ of 1 mol dm⁻³ barium hydroxide producing a precipitate of barium sulfate.

H₂SO₄(aq) + Ba(OH)₂(aq) → 2H₂O (l) + BaSO₄(s)

Which graph represents a plot of conductivity against volume of acid added?

Use the graph to deduce the dependence of the reaction rate on the amount of Mg.

In a laboratory experiment solutions of potassium iodide and hydrogen peroxide were mixed and the volume of oxygen generated was recorded. The volume was adjusted to 0 at t = 0.

The data for the first trial is given below.

Plot a graph on the axes below and from it determine the average rate of
formation of oxygen gas in cm³ O₂ (g) s⁻¹.

Average rate of reaction:

Describe the density trend across periods 4 and 5 of the periodic table.

Compare the ease of oxidation of s-block and d-block metals to their melting points and densities. Use section 25 of the data booklet.

The dotted line represents the formation of oxygen, O₂ (g), from the uncatalysed complete decomposition of hydrogen peroxide, H₂O₂ (aq).

Which curve represents a catalysed reaction under the same conditions?

In a laboratory experiment solutions of potassium iodide and hydrogen peroxide were mixed and the volume of oxygen generated was recorded. The volume was adjusted to 0 at t = 0.

The data for the first trial is given below.

Plot a graph on the axes below and from it determine the average rate of formation of oxygen gas in cm³ O₂ (g) s⁻¹.

Average rate of reaction:

Compare the ease of oxidation of s-block and d-block metals to their melting points and densities. Use section 25 of the data booklet.

Describe the density trend across periods 4 and 5 of the periodic table.

Data collected from a larger number of silicon samples could also be plotted to determine the density using the following axes.

Which statements are correct?

    I. The density is the slope of the graph.
    II. The data will show that mass is proportional to volume.
    III. The best-fit line should pass through the origin.

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

The dotted line represents the formation of oxygen, O₂(g), from the uncatalysed complete decomposition of hydrogen peroxide, H₂O₂ (aq).

Which curve represents a catalysed reaction under the same conditions?

Determine the initial rate of reaction of limestone with nitric acid from the graph.

Show your working on the graph and include the units of the initial rate.