DP Chemistry Questionbank

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.

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.

Deduce why the temperature is higher in mixture C than in mixture D.

Suggest one disadvantage of using this smoke in an enclosed space.

Deduce why more heat was produced in mixture B than in mixture A.

Some oxides of period 3, such as Na₂O and P₄O₁₀, react with water. A spatula measure of each oxide was added to a separate 100 cm³ flask containing distilled water and a few drops of bromothymol blue indicator.

The indicator is listed in section 22 of the data booklet.

Deduce the colour of the resulting solution and the chemical formula of the product formed after reaction with water for each oxide.

State a technique other than a pH titration that can be used to detect the equivalence point.

Which substance will not produce copper(II) chloride when added to dilute hydrochloric acid?

A.  $\mathrm{Cu} \left(\mathrm{s}\right)$

B.  $\mathrm{Cu}\left(\mathrm{OH}{)}_2 \right(\mathrm{s})$

C.  ${\mathrm{CuCO}}_3 \left(\mathrm{s}\right)$

D.  $\mathrm{CuO} \left(\mathrm{s}\right)$

State the $K_{\mathrm{a}}$ expression for ethanoic acid.

Potassium hydroxide solutions can react with carbon dioxide from the air. The solution was made one day prior to using it in the titration.

Predict, giving a reason, the effect of this error on the calculated concentration of ethanoic acid in 5(e).

An additional experiment was conducted in which only the sulfuric acid catalyst was titrated with $\mathrm{NaOH}\hspace{0.17em}\left(\mathrm{aq}\right)$. Outline why this experiment was necessary.

State an equation for the reaction of magnesium hydroxide with hydrochloric acid.

Outline, using an equation, why sodium ethanoate is basic.

Activity series of selected elements:

$$\text{greatest activity}\stackrel{\text{K, Ca, Al, Fe, H, Cu, Ag, Au}}{\leftarrow }\text{least activity}$$

Which react with dilute sulfuric acid?

       I.     Cu

       II.     CuO

       III.     CuCO₃

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

What happens to the amount of hydroxide ions and hydroxide ion concentration when water is added to a solution of NH₃(aq)?

Deduce, giving reasons, whether the reaction of magnesium nitride with water is an acid–base reaction, a redox reaction, neither or both.

Deduce, giving reasons, whether the reaction of magnesium nitride with water is an acid–base reaction, a redox reaction, neither or both.

With which do most acids react?

   I. sodium hydrogen carbonate
   II. magnesium
   III. calcium sulfate

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

An antacid contains calcium carbonate and magnesium carbonate.

Write the equation for the reaction of magnesium carbonate with excess stomach acid.