Chemical changes

This question is about acids and alkalis. Acids and alkalis are substances that produce ions in aqueous solution. Which ion is always produced by an acid in aqueous solution?

Which ion is always produced by an alkali in aqueous solution?

What type of aqueous solution has a pH of 11?

A student determined the reacting volumes of hydrochloric acid and sodium hydroxide solution by titration. The method involved measuring 25.0 cm³ of the sodium hydroxide solution. Which piece of equipment should be used to measure 25.0 cm³ of the sodium hydroxide solution in step 1?

In the titration method, the student adds the hydrochloric acid drop by drop until the indicator changes colour. Which piece of equipment should be used to add the hydrochloric acid drop by drop in step 4?

Which is the anomalous result in Table 1? <br/><br/> <table border="1" cellpadding="12" cellspacing="0" style="border-collapse: collapse; font-family: Arial, sans-serif; font-size: 15px; border: 2px solid black;"> <caption style="font-weight: bold; font-size: 16px; margin-bottom: 10px;">Table 1</caption> <tr> <th style="border: 1px solid black; padding: 12px; text-align: left; font-weight: bold;">Trial</th> <th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">1</th> <th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">2</th> <th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">3</th> <th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">4</th> </tr> <tr> <td style="border: 1px solid black; padding: 12px; font-weight: bold;">Volume of hydrochloric acid<br/>added in cm³</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">24.3</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">24.5</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">28.1</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">24.4</td> </tr> </table> <br/><br/>

Suggest one reason for the anomalous result in Table 1.

Figure 7 shows a piece of sodium being added to water. Give two observations that could be seen when sodium is added to water.

Give one reason why molten sodium chloride conducts electricity. Refer to ions in your answer.

Table 3 shows products of the electrolysis of two molten ionic compounds. Complete Table 3. <br/><br/> <table border="1" cellpadding="12" cellspacing="0" style="border-collapse: collapse; font-family: Arial, sans-serif; font-size: 14px; border: 2px solid black;"> <caption style="font-weight: bold; font-size: 16px; margin-bottom: 10px;">Table 3</caption> <tr> <th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">Molten compound</th> <th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">Product at the negative<br/>electrode</th> <th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">Product at the positive<br/>electrode</th> </tr> <tr> <td style="border: 1px solid black; padding: 12px;">Magnesium bromide</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">Magnesium</td> <td style="border: 1px solid black; padding: 12px; text-align: center;"></td> </tr> <tr> <td style="border: 1px solid black; padding: 12px;">Potassium chloride</td> <td style="border: 1px solid black; padding: 12px; text-align: center;"></td> <td style="border: 1px solid black; padding: 12px; text-align: center;">Chlorine</td> </tr> </table> <br/><br/>

Aluminium is extracted by electrolysis. The electrolyte is a molten mixture of aluminium oxide and cryolite. Why is a mixture used instead of pure aluminium oxide as the electrolyte?

Electrolysis of an aqueous solution of sodium sulfate produces hydrogen and oxygen. What is the source of the hydrogen and the oxygen produced during the electrolysis of aqueous sodium sulfate solution?

Why is hydrogen produced instead of sodium in the electrolysis of aqueous sodium sulfate solution?

Figure 9 shows the relationship between the volume of hydrogen and the volume of oxygen produced during the electrolysis. Give one conclusion that can be made about the volume of hydrogen produced compared to the volume of oxygen produced.

This question is about displacement reactions. Iron is extracted from iron oxide by a displacement reaction with carbon. Balance the equation for the reaction:\n\nFe₂O₃ + 3C → __ Fe + __ CO

Iron oxide is reduced in this reaction. How does the equation show that iron oxide is reduced?

A student investigated the reactivity of four different metals, A, B, C and D. The student added each metal to aqueous solutions of each of the metal sulfates and observed whether a reaction took place. Give one observation that would show a reaction took place.

Table 4 shows the results. <br/><br/> <table style="border-collapse: collapse; width: 100%; font-family: Arial, sans-serif; text-align: center; border: 2px solid black;"> <thead> <tr> <th colspan="6" style="padding: 10px; font-size: 1.2em; border-bottom: 2px solid black;">Table 4</th> </tr> <tr> <th style="border: 1px solid black; width: 20%;"></th> <th colspan="4" style="border: 1px solid black; padding: 10px; background-color: #f2f2f2;">Metal sulfate solution</th> <th style="border: none; width: 5%;"></th> </tr> <tr style="font-weight: bold;"> <td style="border: 1px solid black; padding: 10px;">Metal</td> <td style="border: 1px solid black; padding: 10px;">A sulfate</td> <td style="border: 1px solid black; padding: 10px;">B sulfate</td> <td style="border: 1px solid black; padding: 10px;">C sulfate</td> <td style="border: 1px solid black; padding: 10px;">D sulfate</td> </tr> </thead> <tbody> <tr> <td style="border: 1px solid black; font-weight: bold; padding: 10px;">A</td> <td style="border: 1px solid black; padding: 10px;">&times;</td> <td style="border: 1px solid black; padding: 10px;">&times;</td> <td style="border: 1px solid black; padding: 10px;">&checkmark;</td> <td style="border: 1px solid black; padding: 10px;">&times;</td> </tr> <tr> <td style="border: 1px solid black; font-weight: bold; padding: 10px;">B</td> <td style="border: 1px solid black; padding: 10px;">&checkmark;</td> <td style="border: 1px solid black; padding: 10px;">&times;</td> <td style="border: 1px solid black; padding: 10px;">&checkmark;</td> <td style="border: 1px solid black; padding: 10px;">&times;</td> </tr> <tr> <td style="border: 1px solid black; font-weight: bold; padding: 10px;">C</td> <td style="border: 1px solid black; padding: 10px;">&times;</td> <td style="border: 1px solid black; padding: 10px;">&times;</td> <td style="border: 1px solid black; padding: 10px;">&times;</td> <td style="border: 1px solid black; padding: 10px;">&times;</td> </tr> <tr> <td style="border: 1px solid black; font-weight: bold; padding: 10px;">D</td> <td style="border: 1px solid black; padding: 10px;">&checkmark;</td> <td style="border: 1px solid black; padding: 10px;">&checkmark;</td> <td style="border: 1px solid black; padding: 10px;">&checkmark;</td> <td style="border: 1px solid black; padding: 10px;">&times;</td> </tr> </tbody> </table> <br/><br/> ✓ shows that a displacement reaction took place, <br/><br/>× shows that a displacement reaction did not take place). <br/><br/>Write metals A, B, C and D in order of reactivity. <br/><br/>Give a reason for your order of reactivity. <br/><br/> Most reactive: _______________ <br/><br/> Least reactive: _______________ <br/><br/> Reason: ______________________

This question is about making a soluble salt. Plan a method to make pure, dry crystals of zinc chloride from zinc carbonate and a dilute acid.

Name two other substances that can each be reacted with a dilute acid to make zinc chloride. Do not refer to zinc carbonate in your answer.

A student produced a salt by reacting copper carbonate with sulfuric acid. This is the method used. 1. Measure 50 cm³ of sulfuric acid into a beaker. 2. Add copper carbonate powder. 3. Stir the mixture. 4. Repeat steps 2 and 3 until copper carbonate is in excess. 5. Filter the mixture. 6. Warm the filtrate gently until crystals start to appear. 7. Leave the solution to cool and crystallise. Complete the word equation for the reaction. copper carbonate + sulfuric acid → ______ + ______ + carbon dioxide

Give one observation the student could make during Step 4 which shows that the copper carbonate is in excess.

Give one reason for filtering the mixture in Step 5.

Name the equipment that can be used to warm the filtrate gently in Step 6.

Some salts can be produced by reacting sulfuric acid with a metal. Neither copper nor sodium is used to produce a salt with sulfuric acid. Give one reason why each metal is not used. Copper: Sodium:

Complete the ionic equation for the reaction between zinc and copper sulfate solution. Include state symbols. Zn(s) + Cu²⁺(aq) → ______ + ______

Solid calcium chloride cannot be electrolysed. Give one reason why.

Name the product formed at the negative electrode when aqueous calcium chloride solution is electrolysed.

What is the half equation for the reaction at the positive electrode when aqueous calcium chloride solution is electrolysed?

A student investigated the electrolysis of green copper chromate solution. Figure 4 shows the apparatus and Figure 5 shows the results. Copper chromate solution contains the ions Cu²⁺ and CrO₄²⁻. Explain the results shown in Figure 5.

A student investigated the voltage produced by different pairs of metal electrodes in a chemical cell. Figure 6 shows the apparatus and Table 3 shows the results. <br/><br/> <table border="1" cellpadding="12" cellspacing="0" style="border-collapse: collapse; font-family: Arial, sans-serif; font-size: 15px; border: 2px solid black;"> <caption style="font-weight: bold; font-size: 18px; margin-bottom: 10px;">Table 3</caption> <tr> <th style="border: 1px solid black; padding: 12px; text-align: left; font-weight: bold;">Electrode A</th> <th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">Symbol of metal</th> <th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">Voltage in volts</th> </tr> <tr> <td style="border: 1px solid black; padding: 12px; font-weight: bold;">Copper</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">Cu</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">−0.59</td> </tr> <tr> <td style="border: 1px solid black; padding: 12px; font-weight: bold;">Magnesium</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">Mg</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">2.12</td> </tr> <tr> <td style="border: 1px solid black; padding: 12px; font-weight: bold;">Nickel</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">Ni</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">0.00</td> </tr> <tr> <td style="border: 1px solid black; padding: 12px; font-weight: bold;">Silver</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">Ag</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">−1.05</td> </tr> <tr> <td style="border: 1px solid black; padding: 12px; font-weight: bold;">Zinc</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">Zn</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">0.51</td> </tr> </table> <br/><br/> This is the method used.<br/><br/> 1. Place a nickel electrode and an electrode made from a different metal (electrode A) in 1.0 mol/dm3 sodium chloride solution.<br/><br/> 2. Measure the voltage produced.<br/><br/> 3. Repeat using different metals for electrode A.<br/><br/> Write the symbols of the five metals in Table 3 in order of reactivity.<br/><br/> Justify your answer.<br/><br/> Most reactive __ __ __ __ __ <br/><br/>Least reactive __ __ __ __ __ <br/><br/> Justification: __ __ __ __ __

The voltage produced by a chemical cell depends on the concentration of the electrolyte solution. Plan an experiment to investigate how the voltage produced by a chemical cell varies with the concentration of the electrolyte solution. The following substances are available: • the metal electrodes in Table 3 • 1.0 mol/dm³ sodium chloride solution • pure water. <br/><br/> <table border="1" cellpadding="12" cellspacing="0" style="border-collapse: collapse; font-family: Arial, sans-serif; font-size: 15px; border: 2px solid black;"> <caption style="font-weight: bold; font-size: 18px; margin-bottom: 10px;">Table 3</caption> <tr> <th style="border: 1px solid black; padding: 12px; text-align: left; font-weight: bold;">Electrode A</th> <th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">Symbol of metal</th> <th style="border: 1px solid black; padding: 12px; text-align: center; font-weight: bold;">Voltage in volts</th> </tr> <tr> <td style="border: 1px solid black; padding: 12px; font-weight: bold;">Copper</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">Cu</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">−0.59</td> </tr> <tr> <td style="border: 1px solid black; padding: 12px; font-weight: bold;">Magnesium</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">Mg</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">2.12</td> </tr> <tr> <td style="border: 1px solid black; padding: 12px; font-weight: bold;">Nickel</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">Ni</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">0.00</td> </tr> <tr> <td style="border: 1px solid black; padding: 12px; font-weight: bold;">Silver</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">Ag</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">−1.05</td> </tr> <tr> <td style="border: 1px solid black; padding: 12px; font-weight: bold;">Zinc</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">Zn</td> <td style="border: 1px solid black; padding: 12px; text-align: center;">0.51</td> </tr> </table> <br/><br/>

Describe how a hydrogen fuel cell produces a potential difference.

This question is about acids and their reactions. Acids can be either weak or strong. What is meant by 'a weak acid'?

Explain what happens to the pH of an acid as the acid is diluted with water.

A student does a titration to find the volume of acid needed to neutralise an alkali. The student fills a burette with the acid. Give three more steps the student must do before adding the acid to the alkali from the burette. You should name any equipment used.

This question is about copper sulfate. Blue copper sulfate turns white when it is heated. The word equation for the reaction is: hydrated copper sulfate ⇌ anhydrous copper sulfate + water (blue) (white) What name is given to hydrated copper sulfate in this reaction? Select one option.

Complete the sentence. The colour change when water is added to anhydrous copper sulfate is white to ______.

This question is about water. Hydrogen gas reacts with oxygen gas to produce water. Water is decomposed into hydrogen gas and oxygen gas using electricity. Which of these words describes the reaction between hydrogen and oxygen gas?

Hydrogen gas reacts with oxygen gas to produce water. Water is decomposed into hydrogen gas and oxygen gas using electricity. Which other word describes the overall process?