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Question 1
A scientist works in a lab that tests samples of vinegar. Vinegar is mainly a mixture of ethanoic acid and water. |
a) | Vinegar needs to have a minimum of 5% acidity in order to be used to preserve food. Calculate how much ethanoic acid needs to be in 25 cm3 of vinegar in order for it to be used to preserve food. Use the equation: percentage acidity = mass of vinegar (g)mass of ethanoic acid (g)× 100 Note that the mass of 1 cm3 of vinegar is 1.01 g.
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b) | The scientist uses a titration to find out how much 1 mol/dm3 sodium hydroxide she needs to add to exactly react with 25.0 cm3 of vinegar. The equation below shows ethanoic acid behaving as an acid. CH3COOH ⇌ CH3COO– + H+ Calculate the minimum volume of sodium hydroxide the scientist uses in her titration. The relative formula mass of CH3COOH is 60.0.
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Question 2
A student tests three different pH meters to find out which pH meter gives the most accurate pH readings. She prepares five solutions, A to E, with different concentrations of hydrogen ions, H+. She dips the pH meters into each solution and takes a reading. The table below shows the student's results. |
a) | Give one letter, A to E, that corresponds to:
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b) | Predict the pH of a solution with a concentration of 1.0 × 10−4 mol/dm3 of hydrogen ions.
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c) | What is the trend in the relationship between concentration of hydrogen ions and pH?
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d) | Which of the statements below best describes a concentrated acid? A The acid is completely ionised in solution in water. B The acid is partially ionised in solution in water. C There is a large amount of acid and a small amount of water. D There is a large amount of water and a small amount of acid.
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e) | Which of the statements below best describes a strong alkali? A The alkali is completely ionised in solution in water. B The alkali is partially ionised in solution in water. C There is a large amount of alkali and a small amount of water. D There is a large amount of water and a small amount of alkali.
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f) | What conclusions can you make about the relative accuracy of each pH meter? Explain each conclusion.
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Question 3
A student does a titration to find the volume of sulfuric acid that reacts with 25 cm3 of potassium hydroxide solution. The image below shows the equipment used. |
a) | 25 cm3 of potassium hydroxide solution is measured with the measuring cylinder. Which piece of equipment could the student use to measure the 25 cm3 more accurately?
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b) | Which of the following ions does sulfuric acid produce in aqueous solution? A H+ B OH- C O2-
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c) | Universal indicator turns purple in potassium hydroxide solution. What is the pH of the solution? A pH 1 B pH 7 C pH 14
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d) | Describe how the student would use the equipment in the image to complete the titration.
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Question 4
The higher the concentration of a sample of dilute acid, the greater the volume of alkali needed to neutralise the acid. The student tested two samples of the same dilute acid, A and B. |
Describe how the student could use titrations to find which sample, A or B, is more concentrated.
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Question 5
Lead nitrate is a salt. A student produces lead nitrate using an acid and a base. |
a) | Which acid should the student use to produce lead nitrate?
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b) | Which of the the following is a base the student could use to produce lead nitrate? A lead chloride B lead oxide C lead sulfate
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c) | Lead nitrate solution mixed with sodium sulfate solution forms lead sulfate as a precipitate. Pb(NO3)2 + Na2SO4 ➔ PbSO4 + 2NaNO3 The method used to make the lead sulfate is:
State and explain two ways of improving this experimental method in order to increase the amount and quality of lead sulfate that could be obtained from 100 cm3 of lead nitrate solution.
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d) | Ammonium nitrate and potassium chloride are both salts. They can be made by neutralisation reactions. Complete the word equations below. ammonia + ➔ ammonium nitrate + water potassium hydroxide + hydrochloric acid → potassium chloride + nitric acid water
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Question 6
Calcium chloride (CaCl2) is a soluble salt. Calcium chloride can be made by reacting dilute hydrochloric acid with either calcium oxide or calcium carbonate. |
a) | Write a balanced symbol equation for the reaction of dilute hydrochloric acid with calcium oxide.
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b) | A student carried out two investigations.
Describe one difference between the two reactions that the student would be able to observe.
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c) | Describe how crystals of calcium chloride can be made from calcium carbonate and dilute hydrochloric acid.
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Question 7
A student dissolved some crystals of an unknown salt in water. The student added sodium hydroxide solution to the salt solution until it was in excess. |
a) | Describe what the student would see if the salt contained calcium ions.
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b) | Would the result predicted in part a) prove that the salt contains calcium ions? Explain your answer.
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c) | Describe an additional test the student could do that would prove the salt contains calcium ions.
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Question 8
Soluble salts are formed by reacting metal oxides with acids. |
a) | Give one other type of substance that can react with an acid to form a soluble salt.
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b) | Copper sulfate contains the ions Cu2+ and SO42-. Give the formula of copper sulfate.
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c) | Describe a method to make pure, dry crystals of copper sulfate, from a metal oxide and a dilute acid.
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Question 9
A student investigates the solubility and pH of metal oxides and non-metal oxides in water. The table shows the student’s results. |
The student concluded that:
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a) | Use information from the table above to explain why the student’s conclusions are only partly correct.
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b) | Give an improved conclusion for metal oxides.
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c) | A student makes crystals of magnesium sulfate using the method below:
Give one reason for each of the following steps:
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d) | Which method should the student use to evaporate the filtrate gently in step 7?
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Question 10
A student makes copper sulphate, CuSO4, by the following general reaction. acid + base ➔ salt + water |
a) | What type of reaction is represented in the equation above?
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b) | The student used copper oxide as the base in the reaction to produce copper sulfate. Name and give the chemical formula of the acid used.
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c) | Explain the purpose of following steps in the student's method. |
c) i) | "Warm the acid."
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c) ii) | "Add copper oxide until it is in excess."
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Question 11
A scientist produces zinc iodide (ZnI2) by following the method below.
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a) | Ethanol is flammable. Suggest how the scientist could evaporate off the ethanol safely.
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b) | Explain why the scientist adds excess zinc rather than excess iodine.
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c) | The equation for the reaction is: Zn + I2 ➔ ZnI2 Calculate the minimum mass of zinc that needs to be added to 1.00 g of iodine so that the iodine fully reacts. (You may need to use a periodic table)
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Question 12
This question is about oxides. The reactions of four different oxides, A, B, C and D, are as follows:
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a) | Identify the acidic, basic, amphoteric and neutral oxide.
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b) | Nitrogen(I) oxide (N2O), nitrogen(II) oxide (NO) and carbon monoxide (CO) are non-metal oxides. They do not react with acids or bases. Which of the following statements is correct? A they are acidic oxides B they are amphoteric oxides C they are basic oxides D they are neutral oxides
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c) | Silicon(IV) oxide (SiO2), has a macromolecular structure. How could you show that SiO2 is acidic and not basic or amphoteric?
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Question 13
This question is about oxides. (You may need to use a periodic table) |
a) | Which of the following statements best describes magnesium oxide? A an acidic oxide formed from a metal B an acidic oxide formed from a non-metal C a basic oxide formed from a metal D a basic oxide formed from a non-metal
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b) | Some magnesium oxide is tested with damp litmus paper. State the final colour of the litmus paper, and identify the ion responsible for this colour.
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c) | Identify an element in period 3 that forms an acidic oxide.
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d) | Zirconium(IV) oxide is an amphoteric oxide. Name a reagent that reacts with both amphoteric oxides, like zirconium(IV) oxide, and acidic oxides.
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Question 14
A student carries out a titration to find out the concentration of a phosphoric acid solution. She reacts sodium hydroxide with the phosphoric acid solution. |
a) | The student states that ‘the titration uses a neutralisation reaction’. Define a neutralisation reaction.
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b) | Which equation represents neutralisation? A 4H+ ➔ 2H2 B H2O ➔ 2H+ + O2– C H+ + OH– ➔ H2O D O2 + H2 ➔ H2O + O2–
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c) | This is the student’s incomplete method for the titration:
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c) i) | The student needs to add another substance to the flask so that she knows when to stop adding the sodium hydroxide. Which substance does the student need to add, and what will she observe?
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c) ii) | The student wants to make sure her final burette reading is as accurate as possible. Describe one way in which the student can make her reading as accurate as possible.
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d) | The student’s repeat readings for her titrations are shown in the table below. The student calculates that the mean titration volume is 20.05 cm3. Explain why the student is correct. Use the information in the table and a calculation in your answer.
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e) | Phosphoric acid contains phosphate ions, PO43−. Phosphoric acid is completely neutralised by sodium hydroxide. What is the formula of the salt that is made? A Na2PO4 B Na3PO4 C Na(PO4)3 D Na2(PO4)3
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Question 15
A student investigates how the pH changes when dilute sodium hydroxide reacts with dilute hydrochloric acid. He places 20.0 cm3 of dilute hydrochloric acid in a beaker. He adds dilute sodium hydroxide to the acid, 1.0 cm3 at a time. He uses a pH meter to measure the pH after each addition of sodium hydroxide. The image below shows a graph plotted with the student's results. |
a) | The student writes an ionic equation for the reaction. H+ + OH– ➔ H2O Use the ionic equation and values from the graph to explain how the pH changes during the reaction.
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b) | The student started with 20.0 cm3 of dilute hydrochloric acid in the beaker. Explain how his results show that the acid is more concentrated than the dilute sodium hydroxide.
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c) | What mass of sodium hydroxide would be needed to make 46.8 g of sodium chloride? (You may need to use a periodic table) A 16 g B 32 g C 50 g D 64 g
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Question 16
The apparatus in the image below can be used in a method to find the volume of hydrochloric acid required to neutralise a solution of sodium hydroxide. |
a) | What is the name given to the method shown in the image above?
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b) | Give the symbol equation for the reaction.
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c) | A student carries out the experiment. His burette readings are shown in the diagram. Use the diagram to give the burette readings to the nearest 0.05 cm3. Give the:
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d) | Calculate the concentration of the hydrochloric acid used. Give your answer to 2 significant figures.
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