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Chemistry AQA
| Question | Answer |
|---|---|
| Explain how fractional distillation can be used to separate a mixture? | Fractional distillation is used to separate components with different boiling points from a mixture. The mixture is heated gradually and each component is collected when it boils. |
| If an element has different isotopes, what does this mean? | Each isotope of an element has the same number of protons but a different number of neutrons in each atom. |
| Complete the gaps in the sentence The centre of the Periodic Table between Groups 2 and 3 contains elements known as the … … . | The centre of the Periodic Table between Groups 2 and 3 contains elements known as the transition metals. |
| Complete the gaps in the sentence Atoms of these elements form … with different charges. | Atoms of these elements form ions with different charges. |
| Complete the gaps in the sentence The compounds formed by these elements are … . | The compounds formed by these elements are coloured |
| Complete the gaps in the sentence They can be used as … to speed up chemical reactions | They can be used as catalysts to speed up chemical reactions. |
| Describe what happens to a metal atom and a non-metal atom when an ionic bond forms between them. | The metal atoms lose electrons to become positively charged ions. The electrons are transferred to the non-metal atoms, which gain electrons to become negatively charged ions. |
| Complete the table. State of substance State symbol solid ( … ) … (l) … (g) ( … ) dissolved in water ( … ) | State of substance State symbol solid (s) liquid (l) gas (g) (aqueous) dissolved in water (aq) |
| What properties of metals make them useful structural materials? | Metals contain metallic bonds, which are very strong. Most metals have high melting and boiling points. |
| Describe what happens when one chlorine atom forms a bond with another chlorine atom. | An electron from each atom is shared so that each atom has a complete outer shell of electrons. |
| Explain why most polymers are solid at room temperature. | The atoms within polymer molecules are held together by strong covalent bonds. The intermolecular forces between the large polymer molecules are also quite strong. |
| Why do chemical symbol equations always need to be balanced? | Mass is conserved. In a chemical reaction, no atoms are made or lost. |
| True or false? A. Three moles of potassium atoms contain a total of just over 18 × 1023 atoms | true: one mole is 6.02 × 10 power 23 atoms, so 3 × 6.02 × 1023 = 18.06 × 10 power23 atoms |
| True or false? Sodium has a lower relative atomic mass than potassium, so three moles of sodium atoms contain fewer than 18 × 10 power 23 atoms | is false: one mole of any element always contains 6.02 × 10 power 23 atoms |
| What is the concentration of 0.5 dm3 solution containing 1.5 moles of hydrochloric acid? | Concentration = amount of substance volume = 1.5 mol 0.5 dm3 = 3 mol/dm3 |
| The following reaction equations show two different ways in which we can produce ethanol. A. C6H12O6 2C2H5OH + 2CO2 B. C2H4 + H2O C2H5OH Which reaction, A or B, has an atom economy of 100%? How do you know this? | Reaction B, because all the reactant atoms end up in the desired product (ethanol). |
| Use these words to complete the sentences that follow. (Use each word once only.) together loses gains In oxidation reactions, a substance often … oxygen. In reduction reactions, a substance often … oxygen. Oxidation and reduction always occur … . | In oxidation reactions, a substance often gains oxygen. In reduction reactions, a substance often loses oxygen. Oxidation and reduction always occur together. |
| Why is the following reaction called a neutralisation reaction? HCl(aq) + KOH(aq) - KCl(aq) + H2O(l) | Hydrochloric acid (HCl) neutralises the alkali potassium hydroxide (KOH). The solution that remains has a pH of 7, meaning that it is neutral. |
| Explain why electrolysis is an expensive way of extracting metals from their ores. | Electrolysis requires a lot of heat and electrical energy. |
| What is the difference between endothermic and exothermic reactions? | Endothermic reactions take in energy from the surroundings and cause a temperature drop. Exothermic reactions give out energy to the surroundings and cause a temperature rise. |
| If a reaction is endothermic, what does this tell us about the energy needed to break and make bonds in the reaction? | An endothermic reaction takes in energy from the surroundings. This means that the energy needed to break bonds is greater than the energy given out by the making of bonds. |
| Choose the correct general formula for alkanes from the following list. CnH2n−2 C2nHn CnH2n CnH2n+2 | CnH2n+2 |
| Which of the following substances are alkenes? CH4 C2H4 C3H8 C4H8 | C2H4 and C4H8 are both alkenes, because they follow the general formula CnH2n |
| The substance with the formula CH3COOH is known as ethanoic acid. This substance is commonly found in vinegar. What is the functional group of ethanoic acid? What would you predict about the pH of vinegar? | The functional group of ethanoic acid is the carboxyl or –COOH group. Vinegar has a pH of less than 7 (it is acidic). |
| Complete the following table that describes tests for different gases. Gas Test for gas … Turns limewater cloudy Hydrogen … Oxygen … … Turns damp indicator paper white | Gas Test for gas Carbon dioxide Turns limewater cloudy Hydrogen Burns with a squeaky pop Oxygen Relights a glowing splint Chlorine Turns damp indicator paper white |
| When calcium carbonate is reacted with hydrochloric acid, calcium chloride is formed along with a colourless gas and a colourless liquid. Name the gas and liquid. Which test could be used to identify the gas? | The gas is carbon dioxide. The liquid is water. Carbon dioxide turns limewater milky. |
| Describe the effects that the evolution of plants had on the Earth’s atmosphere. | Plants use carbon dioxide and water to produce oxygen in the reaction called photosynthesis. As more plants evolved, the amount of oxygen in the atmosphere increased. Eventually the levels of oxygen were enough for land-based animals that breathed oxyge |
| What is the carbon footprint? | The carbon footprint of a product, service or event is the total amount of carbon dioxide and other greenhouse gases that are emitted over its full life cycle |
| Why can’t we release our waste water directly into the environment? | Waste water can contain toxic chemicals, harmful microorganisms and other organic matter. All these things can cause pollution and affect plants and animals, including humans. |
| What is the purpose of a life cycle assessment? | A life cycle assessment provides a way of comparing different products to see which cause least damage to the environment, over their whole lifetime. |
| Explain the conditions used in practice in the Haber process to produce ammonia | The Haber process involves an equilibrium reaction that is exothermic. A moderate temperature is used to give a balance between a fast rate but low yield of ammonia, and a slow rate but high yield. A high pressure produces a high yield. An iron cataly |
Created by:
davidmitch
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