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CC9,10F
GCSE Combined Science Chemistry
| Question | Answer |
|---|---|
| What is empirical formula? | The simplest whole number ratio of atoms or ions of each element in a substace |
| What are the 2 stages for working out empirical formula? | 1) Divide the masses by relative atomic masses. 2) Divide all the answers by the smallest number. |
| What is molecular formula? | The actual number of atoms of each element in one molecule |
| What are the 2 steps in calculating molecular formula from empirical formula? | 1) Work out the relative mass of the empirical formula 2) divide the molecular formula mass by the empirical formula mass. |
| What is relative formula mass? | The sum of the relative atomic masses of all atoms or ions in its formula |
| What is the law of conservation of mass? | The mass of the reactants is equal to the mass of the products |
| What is concentration? | The amount of solute dissolved in a solution |
| What is the equation for calculating concentration | Amount of solute (g)/ Volume of solution (dm3) |
| What is produced during the electrolysis of molten lead bromide? | Molten lead and bromine gas. |
| What name is given to a positively charged ion and the negatively charged ion? | Cation(Positive) Anion (Negative) |
| What type of substance tends to form cations and anions? | Cations - metals and hydrogen Anions - non-metals |
| Which electrical supply is used in electrolysis? | Direct Current |
| What happens to compounds during electrolysis? | The decompose(break down) |
| Which electrode are positively charged ions and negatively charged ions attracted to? | Positive ions - Cathode Negative ions - Anode |
| What happens at the anode and the cathode? | They form neutral particles. At the anode the anion loses electrons. At the cathode the cation gains electrons. |
| What is an electrolyte? | An ionic compound that is either molten or dissolved in water. |
| Explain electrolysis in terms of electron movement. | The anion loses electrons at the anode, these travel to the power source and then go to the cathode where they are gained by the cation. |
| What is the difference between the electrolysis of a molten compound and that of a compound in aqueous solution? | When a molten compound is electrolysed only the ions from the compound itself are involved. When an aqueous compound is electrolysed the hydrogen and hydroxide ions from the water are also involved. |
| What positive and negative ions are present in copper sulphate solution? | Cu2+, SO42-, OH-, H+ |
| Which ion is discharged the most and the least readily out of OH-, SO42- and Cl-? | Most readily - Cl- Least readily - SO42- |
| Which ion is discharged the most and the least readily out of Na+, H+ and Cu2+? | Most readily - Cu2+ Least readily - Na+ |
| What inert material are electrodes made from? | Graphite |
| What is produced during the electrolysis of copper chloride solution? | Copper, chlorine and water |
| What is produced during the electrolysis of copper sulphate solution? | Copper, oxygen and sulphuric acid |
| What is produced during the electrolysis of sodium sulphate solution? | Hydrogen, oxygen and sodium sulphate |
| What is produced during the electrolysis of sodium chloride solution? | Hydrogen, chlorine and sodium hydroxide |
| What is the relationship between the amount of hydrogen and oxygen produced in the electrolysis of water? | The amount of hydrogen is always double the amount of oxygen. |
| What happens at the anode when copper electrodes are used in the electrolysis of copper sulphate solution? | Copper atoms lose electrons and turn into ions which go into the solution. The anode gets smaller. |
| What happens at the cathode when copper electrodes are used in the electrolysis of copper sulphate solution? | Copper ions gain electrons and turn into atoms. The cathode gets bigger. |
| Electrolysis is used to purify copper. What is the difference in the copper used at each electrode? | The anode is made of impure copper and the cathode is made of pure copper. |
| Magnesium carbonate is insoluble. What do you need to do before it will conduct electricity? | Melt it |
| Sodium fluoride is soluble. Explain what the easiest way for it to conduct electricity is | Dissolve it in water because this does not require high temperatures |
| Which ions are in NaCl | Na⁺ and Cl⁻ |
| Which ions are in CuCl₂ | Cu²⁺ and two Cl⁻ |
| Which ions are in Na₂SO₄ | 2 ions of Na⁺ and one SO₄²⁻ |
| What is electrolysis? | Using a dc electric current to decompose (break down) a substance |
| What is an electrolyte? | An ionic compound in the molten state or dissolved in water |
| What happens to an ionic substance when it is melted or dissolved in water? | The ions become free to move around |
| What is the name for the positive electrode? | The anode |
| What is the name for the negative electrode? | The cathode |
| Do positive ions move to the anode or the cathode? | Cathode |
| Do negative ions move to the anode or the cathode? | Anode |
| What will be the products for the electrolysis of molten iron bromide? | Iron and bromine |
| What will be the products for the electrolysis of molten zinc oxide? | Zinc and oxygen |
| What will be the products for the electrolysis of sodium sulfate solution? | Hydrogen gas and Oxygen gas |
| What will be the products for the electrolysis of acidified water? | Hydrogen gas and Oxygen gas |
| What happens to the change in mass of the electrodes if you increase the current? | As current increases so does the change in mass. |
| When copper sulphate solution is electrolysed using copper electrodes. What happens to the mass of the electrodes? | The cathode mass increases. The anode mass decreases. |
| Why use propanone to dry the electrodes when reweighing them after the electrolysis. | It evaporates drying the electrodes, no need to physically dry them. |
| What will be the products for the electrolysis of copper chloride solution? | Copper and chlorine |
| What will be the products for the electrolysis of molten lead bromide? | lead and bromine |
| In the electrolysis of sodium chloride solution, what are the products? | Chlorine gas and hydrogen gas |
| Why is sodium not produced in the electrolysis of sodium chloride solution? | It is more reactive than hydrogen so hydrogen is produced instead. |
| What is produced at the anode in electrolysis of solutions? | Either a halogen or oxygen (when there is no halogen present) |
| For the extraction of which metals is electrolysis needed? | Ones more reactive than carbon, e.g. aluminium |
Created by:
Davenant Foundation School
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