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What are the products at the electrodes when dilute sulfuric acid is electrolysed using inert electrodes?
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Describes the electrolysis of molten potassium bromide?
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IGCSE CHEMISTRY
CHAPTER 5
| Question | Answer |
|---|---|
| What are the products at the electrodes when dilute sulfuric acid is electrolysed using inert electrodes? | Anode - Oxygen Cathode - Hydrogen |
| Describes the electrolysis of molten potassium bromide? | Product of Anode - Bromine Product of cathode - Potasium |
| A section of an overhead power cable. Explains why a particular substance is used | Aluminium has a low density and is a good conductor of electricity |
| What are the electrode products when molten silver iodide is electrolysed between inert electrodes? | Cathods - Silver Anode - iodine |
| Copper and hydrogen can each be formed by electrolysis. At which electrodes are these elements formed? | Copper - Cathods Hydrogen - Cathods |
| Which action will plate the pan with copper? | Making the pan the cathode and the copper the anode |
| An object is electroplated with silver using an aqueous silver salt as the electrolyte. Which set of conditions is used? | The object to be electroplated is the cathode The other electrode is made from Silver |
| Which metal could not be used for electroplating by using an aqueous solution? | Sodium |
| Which products are formed at the electrodes when a concentrated solution of sodium chloride is electrolysed? | Cathode - Hydrogen Anode - Chlorine |
| A student wishes to electroplate an object with copper. What must he do? | The object is made the cathode |
| Which substance will not conduct electricity? | Plastic |
| Which products are formed at the anode and cathode when electricity is passed through molten lead(II) bromide? | Anode - Bromine molecules Cathode - Lead atoms |
| What will be produced at the anode and at the cathode, if molten potassium chloride is electrolysed? | Anode - Chlorine Cathode - Potassium |
| Which substance causes the lamp to light when added to the glass tube? | Aqueous sodium chloride |
| Some white anhydrous copper(II) sulfate powder is put into a beaker of water and stirred. What would show that the process was exothermic? | The beaker feels warmer |
| Name one statement about the electrode products> | Gases were given off at the cathode |
| In separate experiments, electricity was passed through concentrated aqueous sodium chloride and molten lead bromide. What would happen in both experiments? | A halogen would be formed at the anode. |
| Describes the colours of the gases at the electrodes? | Anode - Yellow-green Cathode - Colourless |
| A section of an overhead power cable. Explains why a particular substance is used? | A Aluminium has a low density and is a good conductor of electricity |
| Metals could be extracted from their molten chlorides using electrolysis. Which substances are formed at each electrode? | Anode - Chlorine Cathode - Metal |
| Electricity from a power station passes through overhead cables to a substation and then to a school to used electrolyse concentrated hydrochloric acid using inert electrodes. Which substances are used for the overhead cables and the electrodes? | Overhead cables - Aluminium Electrodes - Platinum |
| Name one statement about the electrolysis of molten lead(II) bromide? | A red / brown gas is seen at the anode |
| What is the test for the gas formed at the positive electrode? | Bleaches damp litmus paper |
| Aluminium is extracted from its oxide by electrolysis. The oxide is dissolved in ……1…… cryolite and aluminium is deposited at the ……2…… | 1. Molten 2. Cathode |
| The chemical process taking place on the surface of the object is Cu2+(aq) + 2e– Cu(s) Explain whether this process is oxidation or reduction. | Red and (the Cu ion copper ions) is gaining electrons is decreasing in oxidation number |
| Give two changes which would be needed in order to coat nickel onto the object | Replace (anode of) copper with nickel; Replace electrolyte with nickel(II) sulfate / NiSO4; |
| Copper, nickel and silver are transition elements. Typical physical properties of transition elements are a high density and a high melting point. Give three different properties of transition metals which are not typical of other metals | (Good) catalysts; Variable oxidation numbers; Form coloured compounds / coloured ions; |
| Aluminium is extracted by the electrolysis of a molten mixture contains aluminium oxide, This decomposes to form aluminium at the negative electrode and oxygen at the positive electrode. Write an ionic equation for the reaction at the negative electrode | Al 3+ + 3e → Al formula of Al 3+ ion |
| Aluminium is extracted by the electrolysis of a molten mixture contains aluminium oxide, This decomposes to form aluminium at the negative electrode and oxygen at the positive electrode. Is the reaction exothermic or endothermic? | Endothermic Electrical energy supplied |
| Explain 3 points why the mass of the magnesium electrode decreases and the mass of the copper electrode increases. | Magnesium forms ions (in solution Magnesium loses electrons Magnesium is oxidised |
| How could you use this cell to determine which is the more reactive metal, magnesium or manganese? | M1 set up a magnesium / manganese cell; M2 the negative electrode (is the more reactive) OR the electrode that loses mass (is more reactive); |
| The combustion of propane, C3H8, is exothermic. Give an equation for the complete combustion of propane | 3H8 + 5O2 → 3CO2 + 4H2O |
| Photosynthesis is an unusual endothermic reaction. Where does the energy for photosynthesis come from? | Light from the sun |
| Photosynthesis is an unusual endothermic reaction. Give the word equation for photosynthesis | Carbon dioxide + water Glucose + oxygen |
| Zinc is an important metal. Its uses include making alloys and the construction of dry cells (batteries). Name an alloy which contains zinc | Brass |
| Zinc is an important metal. Its uses include making alloys and the construction of dry cells (batteries). What is the other metal in this alloy? | Copper |
| The main ore of zinc is zinc blende, ZnS. The ore is heated in the presence of air to form zinc oxide and sulfur dioxide. Write the equation for this reaction. | 2ZnS + 3O2 € 2ZnO + 2SO2 |
| The main ore of zinc is zinc blende, ZnS Give four major use of sulfur dioxide | Manufacture of sulfuric acid Bleach or making wood pulp or making paperfood or fruit juice or Wine preservative Fumigant or sterilising |
| Zinc can be obtained from zinc oxide. Aqueous zinc sulfate is made from zinc oxide and the solution is electrolysed with inert electrodes. Name the reagent which will react with zinc oxide to form zinc sulfate. | Sulfuric acid |
| Write the equation for the reaction at the negative electrode | Zn2+ + 2e Zn |
| Name the product at the positive electrode. | Oxygen |
| The electrolyte changes from zinc sulfate to ...... | Sulfuric acid |
| Write the equation for the chemical reaction that takes place in a hydrogen fuel cell. | 2H2 + O2 → 2H2O |
| At which electrode does oxidation occur? Explain your choice | Anode Negative electrode and electrons lost |
| Write an ionic equation for the reaction at this electrode | H2 → 2H + 2e( ) / H2 – 2e( ) → 2H / H2 + 2OH → 2H2O + 2e( ) / H2 + 2OH – 2e( ) → 2H2O |
| Fuel cells are used to propel cars. Give two advantages of a fuel cell over a gasoline-fuelled engine | lightweight quieter |
| What is the disadvantage of using a high pressure for the reaction | High pressure reduces yield High pressure plant is expensive |
| Chlorine is made by the electrolysis of concentrated aqueous sodium chloride. Describe this electrolysis. Write ionic equations for the reactions at the electrodes and name the sodium compound formed. | Hydrogen and chlorine / H2 and Cl2 Sodium hydroxide / NaOH / Na OH |
| Aluminium is obtained from purified alumina, Al 2O3, by electrolysis. Alumina is obtained from the main ore of aluminium. State the name of this ore. | Bauxite |
| Describe six extraction of aluminum from alumina. Include the electrolyte, the electrodes and the reactions at the electrodes. | Electrolyte aluminum dissolved in molten cryolite Use cryolite to reduce mp Electrodes carbon Aluminum formed at cathode Oxygen formed at anode Anode burns |
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