AQA GCSE.docx

Describe the plum pudding model of the atom - correct answer A ball of positive charge with randomly embedded negatively charged electrons in it. Atom contains electrons, protons and neutrons. Write the three particles in order - correct answer ron n on Predict outer shells of tennessine - correct answer Number of outer shells: 7 Reason: it is in group 7 Why tennessine was not accepted as a new element by other scientists until 2015 - correct answer Time needed for peer review Plan a method to obtain pure dry crystals of zinc chloride from zinc carbonate and a dilute acid - correct answer 1. Add zinc carbonate to conical flask containing hydrochloric acid. 2. Keep adding solid until in excess. 3. Filter the mixture to remove excess zinc carbonate. 4. Heat the zinc carbonate mixture to crystallisation point using an electric heater or water bath. 5. Leave solution to crystallise. 6. Pat formed crystals dry with filter paper Two other substances that can be reacted with dilute acid to form zinc chloride - correct answer 1. Zinc carbonate. 2. Zinc hydroxide 3. Zinc oxide 4. Zinc Explain why methane and poly (ethene) exist in different states at room temperature - correct answer Methane consists of much smaller molecules therefore it has weaker intermolecular forces needing less energy to overcome, therefore the boiling point is lower and remains in gaseous state. However poly(ethene) consists of larger molecules and has stronger intermolecular forces requiring higher energy to overcome. Therefore, the boiling point of poly(ethene) is much higher and it remains in solid state. What is meant by a weak acid? - correct answer The acid only partially ionises, does not fully dissociate in an aqueous solution Name an indicator that can be used in titration. Give the colour change of indicator when acid from burette is added to alkali in flask - correct answer Name of indicator: phenolpthalein Colour change: pink - colourless Or Name of indicator: damp litmus paper Colour change: blue to red Give formula of ion which makes a solution alkaline - correct answer OH- A solution of hydrochloric acid has a pH of 4.5 has a concentration of H+ ions of 3.16 * 10-5 mol/dm3 What is concentration of H+ ions in a solution of hydrochloric acid with pH 2.5? - correct answer Concentration of H+ ions = 3.16 * 10-3