Titrations

A student makes some ammonium sulfate solution by using a titration.

Which pair of solutions should be used to make the ammonium sulfate solution?

The student uses the following apparatus to make the solution of ammonium sulfate.

Draw one straight line from each apparatus name to the diagram of the apparatus.

In this titration, the student uses methyl orange as the indicator.

Explain why an indicator is used in a titration.

The student carries out a rough titration first.

Figure 9 shows the burette readings at the start and at the end of the titration.

At the start of the titration, the burette reading is 2.15 cm³.

Give the reading on the burette at the end of the titration.

The student carries out accurate titrations to obtain concordant results.

Figure 10 shows the volume of solution delivered by the burette in the three accurate titrations.

Circle the volumes the student should use to calculate the mean volume.

Using the volumes that you have circled, calculate the mean volume of solution delivered by the burette.

mean volume of solution =_........ cm³

A student is asked to carry out a titration to find the concentration of a sodium hydroxide solution.

A teacher dilutes some sulfuric acid with distilled water to make a solution with a concentration of 0.250 mol dm^–3 for the student to use.

What effect does diluting the sulfuric acid with distilled water have on the pH of the solution and the concentration of the H⁺ ions?

What is the concentration, in g dm^–3, of a 0.250 mol dm^–3 solution of H₂SO₄?

(relative formula mass: H₂SO₄ = 98.0)

The student uses the apparatus shown in Figure 10 to carry out the titration.

Before using the apparatus, the student rinses the burette with distilled water.

This is an error.

Explain what effect this error has on the result of the titration.

State what the student should do to correct the error.

*(c) The equation for the reaction in the titration is

Explain how the equation for the reaction and the apparatus in Figure 10 can be used to find the concentration of 25.0 cm³ of sodium hydroxide solution using the 0.250 mol dm^–3 sulfuric acid.

A student was asked to find the volume of lithium hydroxide solution that would react exactly with 25.0 cm³ of dilute hydrochloric acid.

The student used the equipment in Figure 6 to carry out a rough titration and then a further three accurate titrations.

Which is the name of the piece of equipment labelled X in Figure 6?

Describe how the student should measure the 25.0 cm³ of dilute hydrochloric acid accurately into the conical flask.

Figure 7 shows the results of the student’s titrations.

Calculate the volume of lithium hydroxide solution added in the rough titration.

volume of lithium hydroxide solution =_........ ³

Calculate the mean volume of lithium hydroxide solution used in the accurate titrations.

mean volume of lithium hydroxide solution =_........ ³

Methyl orange indicator was added to dilute hydrochloric acid in the conical flask in the titration.

What colour change would be seen in the conical flask at the end point of the titration?

During the titration, lithium hydroxide solution, LiOH, reacts with dilute hydrochloric acid, HC l, to form lithium chloride, LiC l, and water.

Write the balanced equation for the reaction.

State the name of this type of reaction.

Titration can be used to find the volume of dilute hydrochloric acid needed to neutralise 25.0 cm³ of barium hydroxide solution.

Before the titration is carried out, the pipette and conical flask are rinsed out with pure water.

Explain the effect, if any, that traces of water in the pipette and conical flask after rinsing could have on the titration result.

pipette

conical flask

In the titration, a few drops of phenolphthalein indicator are added to the barium hydroxide solution.

State the change in colour of phenolphthalein at the end point, when the barium hydroxide solution has just been neutralised.

Write the ionic equation for the neutralisation reaction that occurs when hydrochloric acid is added to barium hydroxide solution.

When barium hydroxide solution is neutralised by dilute sulfuric acid, a white precipitate of barium sulfate is formed in the conical flask.

Describe an experiment to obtain a sample of pure, dry barium sulfate from the contents of the conical flask.

Titration is used to carry out some neutralisation reactions.

Ammonium nitrate can be made by neutralisation.

State the name of the two reactants that are neutralised to make the salt ammonium nitrate.

Ammonium nitrate is a fertiliser. Another fertiliser is ammonium phosphate.

Which elements are combined in ammonium phosphate?

Titrations involve aqueous solutions and the use of burettes.

Figure 8 shows readings on part of a burette at the start and at the end of a titration.

Calculate the volume of solution added from this burette.

Give your answer to a suitable number of decimal places.

A student carries out a titration four times.

The volumes from the student’s results table are shown in Figure 9.

Tick the volumes that should be used to calculate the mean volume.

Figure 10 shows the burette and flask prepared for use by the student. The burette is supported vertically by a clamp that is not shown in the diagram.

The student wrote a description of how they used the burette.

Give three improvements to the way that the student used the burette.

In a titration a student placed alkali in the flask.

By mistake a few drops of litmus and a few drops of phenolphthalein were added to the flask.

The student added acid to the flask until the mixture was acidic.

Predict the colour change that would be seen.

In a titration a student rinsed out the flask with distilled water and did not dry it.

They used the flask for titration, adding the solution from the burette until the indicator changed colour.

State the effect, if any, on the titre volume of using the wet flask rather than a dry flask.

A student wanted to find the volume of dilute hydrochloric acid that would react with 25.0 cm³ of lithium hydroxide solution.

They used the equipment in Figure 7 to carry out a rough titration and then a further two accurate titrations.

Suggest why the student carried out a rough titration before the two accurate titrations.

Figure 8 shows the results of the rough titration.

What was the volume of acid added in the rough titration?

Describe how the rough titration should be carried out once the dilute hydrochloric acid, lithium hydroxide solution and indicator are placed in the apparatus in Figure 7.

Which is the name of an indicator that is suitable to use in this titration?

During the titration the dilute hydrochloric acid, HC l, is reacting with the lithium hydroxide solution, LiOH.

Explain what type of reaction is taking place in the titration.

The volume of dilute sulfuric acid required to neutralise 25.0 cm³ of ammonia solution can be found by titration.

In the titration, a few drops of methyl orange indicator were added to the ammonia solution in a conical flask before adding the dilute sulfuric acid.

State the change in colour of the methyl orange at the end point when the ammonia solution has just been neutralised.

When the ammonia solution was neutralised by the dilute sulfuric acid, a solution of ammonium sulfate was formed.

Complete the balanced equation for the reaction between ammonia solution and sulfuric acid.

The titration was repeated to obtain a mean volume of dilute sulfuric acid required to neutralise the 25.0 cm³ of ammonia solution. The volumes of the two solutions were measured accurately.

Explain two other practical steps that should be used in the titration to ensure that an accurate titre volume is obtained.

The mean volume of dilute sulfuric acid required to neutralise the ammonia solution was determined from the results of the titration.

This volume of dilute sulfuric acid was added to 25.0 cm³ of ammonia solution in a conical flask.

Devise a plan to produce a sample of dry ammonium sulfate from the contents of the conical flask.

Fertilisers are sometimes added to soil.

State why fertilisers are added to soil.

Fertilisers contain compounds of different elements. Three of these elements have the symbols K, N and P.

Use the periodic table to state the names of these three elements.

The fertiliser ammonium sulfate may be made by titrating ammonia solution with dilute sulfuric acid.

Three pieces of apparatus, P, Q and R, used to measure volumes of liquid are shown in Figure 1.

Give the names of the pieces of apparatus P and Q.

In the titration experiment, small volumes of dilute sulfuric acid are added gradually to the ammonia solution in a flask.

Give the letter, P, Q or R, of the piece of apparatus in Figure 1 that should be used to add the dilute sulfuric acid.

The titration experiment is used to produce a solution of ammonium sulfate.

Describe how solid ammonium sulfate should be obtained from this solution.

A sample of solid potassium hydroxide contained soluble, unreactive impurities.

A student tried to find the mass of potassium hydroxide in the sample, using the following method.

step 1 measure the mass of the sample of impure potassium hydroxide

step 2dissolve the sample in 250 cm³ of water in a beaker

step 3take a 25 cm³ sample of the potassium hydroxide solution using a measuring cylinder and pour into a conical flask

step 4 add 3 drops of indicator to the solution

step 5 put the conical flask on a white tile

step 6 using a burette, add dilute sulfuric acid of known concentration drop by drop to the solution, while swirling the flask

step 7 continue adding the sulfuric acid until the colour of the solution changes

step 8 record the volume of sulfuric acid added

step 9 use this result to calculate the mass of pure potassium hydroxide in the sample.

Suggest three ways to improve this method to obtain a more accurate mass of pure potassium hydroxide.

The indicator used was phenolphthalein.

Which row shows the colour change that would be seen in this titration?

Another student carried out the titration accurately.

12.15 cm³ of dilute sulfuric acid with a concentration of 0.140 mol dm^–3 reacted completely with 25.00 cm³ of potassium hydroxide solution.

Calculate the concentration of this potassium hydroxide solution.

concentration of potassium hydroxide solution =_........ mol dm

A different solution of potassium hydroxide had a concentration of 0.175 mol dm^–3.

This potassium hydroxide solution was made by dissolving 2.56 g of impure potassium hydroxide to form 250 cm³ of solution.

Calculate the percentage by mass of potassium hydroxide in the impure potassium hydroxide.

(relative formula mass: KOH = 56.0)

percentage by mass of potassium hydroxide =_........

Potassium hydroxide reacts with hydrochloric acid to form potassium chloride and water.

potassium hydroxide + hydrochloric acid potassium chloride + water

A student carried out a titration to find the exact volume of dilute hydrochloric acid that reacted with 25.0 cm³ of potassium hydroxide solution.

There were five steps in the titration. The steps shown are not in the correct order.

step J pour the potassium hydroxide solution into a conical flask and add a few drops of indicator to this solution step K fill a burette with the dilute hydrochloric acid and record the initial reading from the burette step L use a measuring cylinder to obtain 25 cm³ of potassium hydroxide solution step M take a final reading from the burette and calculate the volume of the dilute hydrochloric acid reacted step N run the dilute hydrochloric acid from the burette into the conical flask until the indicator changes colour

Write the steps in the correct order.

Some of the steps have been completed for you.

first step last step

Suggest an alternative piece of apparatus that could be used in step L to obtain exactly 25.0 cm³ of potassium hydroxide solution.

A student was then asked to produce a pure sample of solid potassium chloride.

After finding the volume of acid reacted in step M, the student added this volume of acid to a fresh 25.0 cm³ sample of the potassium hydroxide solution. This mixture was then evaporated.

Explain why this new mixture was evaporated rather than the original mixture from the titration, to produce a pure sample of solid potassium chloride.

After evaporation, the mass of the potassium chloride was determined.

The theoretical yield of the experiment was 0.70 g. The actual yield was 0.84 g.

This gave a percentage yield greater than 100%.

Calculate the percentage yield of this experiment.

percentage yield =_........

Suggest a reason why the actual yield was greater than the theoretical yield.

The equation for the reaction between potassium hydroxide solution and dilute hydrochloric acid is

Calculate the atom economy for the production of potassium chloride from potassium hydroxide and hydrochloric acid. (relative formula masses: KOH = 56.0, HCl = 36.5, KCl = 74.5, H₂O = 18.0)

Give your answer to one decimal place.

atom economy =_........

Potassium hydroxide reacts with hydrochloric acid to form potassium chloride and water.

potassium hydroxide + hydrochloric acid potassium chloride + water

A student carried out a titration to find the exact volume of dilute hydrochloric acid that reacted with 25.0 cm³ of potassium hydroxide solution.

There were five steps in the titration. The steps shown are not in the correct order.

step J pour the potassium hydroxide solution into a conical flask and add a few drops of indicator to this solution step K fill a burette with the dilute hydrochloric acid and record the initial reading from the burette step L use a measuring cylinder to obtain 25 cm³ of potassium hydroxide solution step M take a final reading from the burette and calculate the volume of the dilute hydrochloric acid reacted step N run the dilute hydrochloric acid from the burette into the conical flask until the indicator changes colour

Write the steps in the correct order.

Some of the steps have been completed for you.

first step
last step

Suggest an alternative piece of apparatus that could be used in step L to obtain exactly 25.0 cm³ of potassium hydroxide solution.

A student was then asked to produce a pure sample of solid potassium chloride.

After finding the volume of acid reacted in step M, the student added this volume of acid to a fresh 25.0 cm³ sample of the potassium hydroxide solution. This mixture was then evaporated.

Explain why this new mixture was evaporated rather than the original mixture from the titration, to produce a pure sample of solid potassium chloride.

After evaporation, the mass of the potassium chloride was determined.

The theoretical yield of the experiment was 0.70 g. The actual yield was 0.84 g.

This gave a percentage yield greater than 100%.

Calculate the percentage yield of this experiment.

Suggest a reason why the actual yield was greater than the theoretical yield.

The equation for the reaction between potassium hydroxide solution and dilute hydrochloric acid is

Calculate the atom economy for the production of potassium chloride from potassium hydroxide and hydrochloric acid. (relative formula masses: KOH = 56.0, HCl = 36.5, KCl = 74.5, H₂O = 18.0)

Give your answer to one decimal place.

(a) A titration of sodium hydroxide solution with hydrochloric acid can be carried out as follows

1 a pipette is used to measure 25.00 cm³ of sodium hydroxide solution into a conical flask 2 a few drops of indicator are added to the sodium hydroxide solution 3 the burette is filled with hydrochloric acid 4 the hydrochloric acid is added to the sodium hydroxide solution until the indicator changes colour.

Describe how the pipette should be used to measure exactly 25.00 cm³ of sodium hydroxide solution into the conical flask.

The burette is first washed with water. It is then rinsed with some of the acid before it is filled with the acid to begin the titration.

Explain why the burette is rinsed with the acid.

Universal indicator solution is not a suitable indicator for an acid-alkali titration.

Give the name of an indicator that is suitable for use in the titration of sodium hydroxide solution with hydrochloric acid.

Universal indicator goes through a series of gradual colour changes as the pH changes in a solution.

Give a reason why universal indicator is not a suitable indicator to use in an acid-alkali titration.

Figure 3 shows some titration results obtained from an experiment in which an alkali is titrated with an acid.

Calculate the accurate volume of acid reacting with the alkali.

accurate volume of acid reacting_........

The concentration of dilute sulfuric acid can be determined by titration with sodium hydroxide solution of known concentration.

25.00 cm³ of dilute sulfuric acid was measured out using a pipette and transferred to a conical flask. A few drops of methyl orange indicator were added to the acid in the conical flask. Sodium hydroxide solution was added to the acid from a burette until the indicator changed colour. The titration was repeated until two concordant results were obtained. The accurate result was the average of the two concordant results.

Describe the colour change seen at the end point of the titration.

A brief report of the practical method has been given above. Further detail can be added to this method to ensure that anyone following the method will obtain an accurate result.

Explain two details that could be added to this practical method to ensure an accurate result is obtained.

In the titration, 25.00 cm³ of dilute sulfuric acid reacted with 24.25 cm³ of 0.200 mol dm⁻³ sodium hydroxide solution, NaOH.

Calculate the concentration of the dilute sulfuric acid, H₂SO₄, in mol dm⁻³.

concentration of sulfuric acid =_........ mol dm

The concentration of some dilute sulfuric acid, H₂SO₄, is 0.250 mol dm⁻³.

Calculate the concentration of sulfuric acid in this solution in g dm⁻³. (relative formula mass: H₂SO₄ = 98)

concentration of sulfuric acid =_........ g dm