Exampro GCSE Chemistry C Chapter higher Name: Class: Author: Date: Time: 56 Marks: 56 Comments: Page of 8
Q. The hip joint sometimes has to be replaced. Early replacement hip joints were made from stainless steel. Stainless steel is an alloy of iron, chromium and nickel. The diagram below represents the particles in stainless steel. Paticle diagram of stainless steal (a) Use the diagram to complete the percentages of metals in this stainless steel. The first one has been done for you. Element Percentage (%) Iron, Fe 7 Chromium, Cr Nickel, Ni (b) Pure iron is a soft, metallic element. (i) Why is iron described as an element?...... () Page of 8
(ii) Pure iron would not be suitable for a replacement hip joint. Suggest why....... () (iii) The three metals in stainless steel have different sized atoms. Stainless steel is harder than pure iron. Explain why............. (Total 6 marks) Q. Hydrogen chloride (HCl) can be made by the reaction of hydrogen (H ) with chlorine (Cl ). (a) The diagrams represent molecules of hydrogen and chlorine. Draw a similar diagram to represent a molecule of hydrogen chloride (HCl). You need show only the outer energy level (shell) electrons. () (b) The word equation for the reaction of hydrogen with chlorine is shown below. hydrogen + chlorine hydrogen chloride Write a balanced symbol equation for this reaction. Page 3 of 8
(c) Hydrogen chloride gas reacts with magnesium to form the ionic compound called magnesium chloride. Use the table of ions on the Data Sheet to help you to write the formula of magnesium chloride. () (d) Why does magnesium chloride have a much higher melting point than hydrogen chloride? (Total 6 marks) Q3. (a) A tin of red kidney beans contains calcium chloride as a firming agent. Calcium chloride is an ionic compound which contains calcium ions (Ca + ) and chloride ions (Cl ). (i) The diagram on the left represents the electronic structure of a chlorine atom. Complete a similar diagram on the right to represent a chloride ion. Page 4 of 8
(i) P 4 +... O P 4 O 0 () (ii) Explain how a calcium atom changes into a calcium ion which has a + charge..... (b) Cola drinks contain phosphoric acid, H 3 PO 4. The two equations show how phosphoric acid can be made from phosphorus. Balance these two equations. (ii) P 4 O 0 +... H O 4H 3 PO 4 () (Total 6 marks) Q4. Ammonia (NH 3 ) is an important chemical which is used to make fertilisers. Ammonia is made from nitrogen and hydrogen, (a) The diagrams represent the electron arrangements in atoms of nitrogen and hydrogen. Complete the diagram showing the arrangement of electrons in a molecule of ammonia. () Page 5 of 8
(b) Name the type of bonding which holds the nitrogen and hydrogen atoms together in an ammonia molecule. () (Total marks) Q5. (a) A piece of lithium is placed on the surface of some water in a beaker. Hydrogen is given off. Lithium hydroxide is also formed. Write a word equation for this reaction. (b) The diagram shows the structure of a molecule of methane. Write down everything that this diagram tells you about a methane molecule. To gain full marks in this question you should write your ideas in good English. Put them into a sensible order and use the correct scientific words. (4) (Total 6 marks) ## Atoms of calcium, phosphorus and fluorine are represented below, each with its mass number and proton number. Page 6 of 8
(a) Use this information to complete the table. CALCIUM PHOSPHOROUS FLUORINE Number of protons in the nucleus 0 9 Number of neutrons in the nucleus 0 6 Number of electrons 5 9 (3) (b) Calcium and fluorine atoms can combine to form the compound calcium fluoride, CaF. The fluoride ion is represented by F. (i) Explain how the fluorine atom forms a fluoride ion. (ii) How is the calcium ion represented? (c) Phosphorus and fluorine form a covalent compound, phosphorus trifluoride. Complete the sentences below which are about this compound. Phosphorus trifluoride is made up of phosphorus and fluorine... These are joined together by sharing pairs of... to form phosphorus trifluoride.... (3) (d) (i) Sodium chloride, an ionic compound, has a high melting point whereas paraffin wax, a molecular compound, melts easily. Explain why. Page 7 of 8
(ii) Molten ionic compounds conduct electricity but molecular compounds are nonconductors, even when liquid. Explain why. (Total 4 marks) Q7. Calcium and magnesium are elements. They are found in the Earth s crust as compounds, often carbonates and sulphates. Magnesium is also found as its chloride. (a) Calcium and magnesium are in the same Group in the Periodic Table. State which Group this is. () (b) Use the Data Sheet to help you to answer this question. (i) Write the chemical formula of magnesium chloride.. () (ii) Name the type of bonding in magnesium chloride.. () (Total 3 marks) Page 8 of 8
Q8. Glass is made from silicon dioxide. Velirina/iStock/Thinkstock (a) Silicon dioxide has a very high melting point. Other substances are added to silicon dioxide to make glass. Glass melts at a lower temperature than silicon dioxide. Suggest why....... () (b) Sodium oxide is one of the substances added to silicon dioxide to make glass. (i) Sodium oxide contains Na + ions and O ions. Give the formula of sodium oxide.... () (ii) Sodium oxide is made by heating sodium metal in oxygen gas. Complete the diagram to show the outer electrons in an oxygen molecule (O ). Page 9 of 8
(c) Glass can be coloured using tiny particles of gold. Gold is a metal. Describe the structure of a metal................... (3) (Total 7 marks) Q9. (a) Write a balanced symbol equation for the reaction between magnesium (Mg) and oxygen (O ) to form magnesium oxide (MgO). () (b) The diagram shows the electronic structure of a magnesium atom. The atomic (proton) number of magnesium is. Magnesium atom Draw a similar diagram to show the electronic structure of an oxygen atom. The atomic (proton) number of oxygen is 8. () Page 0 of 8
(c) Magnesium ions and oxide ions are formed when magnesium reacts with oxygen. The diagram shows the electronic structure of an oxide ion. Oxide ion Draw a similar diagram to show the electronic structure of a magnesium ion. () (d) Magnesium oxide is a white solid with a high melting point. Explain how the ions are held together in solid magnesium oxide. (e) Indigestion tablets can be made from magnesium oxide. The magnesium oxide neutralises some of the hydrochloric acid in the stomach. Complete the word equation for the reaction between magnesium oxide and hydrochloric acid. hydrochloric acid + magnesium oxide... + water. () (Total 6 marks) Page of 8
M. (a) (Chromium =) 0 in correct order (Nickel =) 8 accept Chromium = 8 and Nickel = 0 for mark (b) (i) (because iron is made up of only) one type of atom (ii) not strong allow too soft or too flexible accept it rusts / corrodes or that it could wear away accept could change shape / bend accept layers / atoms could slide (over each other) (iii) structure is different / distorted / disrupted accept not in layers or not regular so it is difficult for layers / atoms / particles to slip / slide (over each other) accept layers cannot slip / slide [6] M. (a) bonding pair in the overlap and 6 other electrons arranged around the chlorine must have either circles or symbols need not be pairs but must not be in the overlap region accept without H and Cl if clear accept all x s or all o s (b) H + Cl HCl accept multiples or fractions accept correct formulae but not balanced for mark correctly balanced equation containing correct lower / upper case symbols gets mark Page of 8
(c) MgCl accept Mg + (Cl - ) (d) because magnesium chloride is made of ions or is ionic accept there are strong forces of attraction between the ions / particles in MgCl or strong electrostatic attractions accept more energy to separate particles in MgCl do not accept MgCl molecules do not accept reference to breaking bonds hydrogen chloride is made of molecules or is covalent accept there are only weak forces of attraction (between the particles / molecules) in HCl do not accept weak covalent bonds do not accept reference to breaking bonds do not accept MgCl is a solid and HCl is a gas [6] M4. (a) all electrons correct (inner shell need not be shown) three bond pairs and two electrons anywhere else can use dots, crosses or e s in any combination (b) covalent accept phonetic spelling do not accept convalent [] M5. (a) LHS lithium + water accept Li and H O accept hydrogen oxide for water RHS hydrogen + lithium hydroxide accept H and LiOH ignore attempts at balancing ignore charges Page 3 of 8
(b) Quality of written communication One mark for the correct use of any three of the terms atom, covalent, bond(ing), saturated, hydrocarbon or alkane any three from: one / the carbon (atom) reject molecules once four hydrogen (atoms) shape / properties neutral CH 4 hydrocarbon saturated / single bond covalent bond / shared electrons alkane reject ionic bond 3 [6] M6. (a) Calcium Phosphorus Fluorine No of protons 5 No of neutrons 0 No of electrons 0 for mark each 3 (b) (i) gain of electron(s) from (atoms) (of) calcium for mark Page 4 of 8
(ii) Ca + gains mark (c) but superscript only Ca + / Ca ++ gains marks atoms electrons molecule(s) not compound each for mark 3 (d) (i) ideas that ionic strong forces between ions molecular weak forces between molecules each for mark (ii) ideas that ionic ions/charged particles are free to move molecular -molecules do not carry a charge each for mark [4] M7. (a) Group / Alkaline Earth Metals for mark (b) (i) MgCl /Mg + (Cl ) (or equation with correct answer) for mark (ii) ionic / electrovalent for mark [3] Page 5 of 8
M8. (a) weaker bonds or allow (other substances) react with the silicon dioxide fewer bonds ignore weaker / fewer forces or disruption to lattice do not accept reference to intermolecular forces / bonds (b) (i) Na O do not accept brackets or charges in the formula (ii) electrons can be shown as dots, crosses, e or any combination (c) bonding pairs accept 4 electrons within the overlap lone pairs on each oxygen accept 4 non-bonding electrons on each oxygen lattice / regular pattern / layers / giant structure / close-packed arrangement (of) positive ions or (of) atoms (with) delocalised / free electrons reference to incorrect particles or incorrect bonding or incorrect structure = max [7] M9. (a) Mg + O MgO accept correct multiples / fractions Page 6 of 8
(b) electrons do not need to be paired accept dots / circles / e instead of crosses do not allow.6 without diagram (c) (d) electrons do not need to be paired allow without bracket s/ must have the charge accept dots / circles / e instead of crosses ignore extra empty outer shells ignore nucleus do not allow [.8] + without diagram oppositely charged (ions / atoms) allow positive and negative(ions / atoms) (they) attract must be in correct context accept held by electrostatic forces ignore ionic bonding maximum if they refer to intermolecular forces / attractions / covalent bonds (e) magnesium chloride accept MgCl (if correctly written) [6] Page 7 of 8
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