GCSE (9 1) Combined Science (Chemistry) A (Gateway Science) J250/03 Paper 3, C1 C3 and CS7 (PAGs C1 C5)

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1 Oxford Cambridge and RSA GCSE (9 1) Combined Science (Chemistry) A (Gateway Science) Paper 3, C1 C3 and CS7 (PAGs C1 C5) (Foundation Tier) Year 11 Test Time allowed: 1 hour 10 minutes F You must have: a ruler (cm/mm) the Data Sheet for GCSE Combined Science A (Chemistry) You may use: a scientific or graphical calculator an HB pencil First name Last name Centre number Candidate number INSTRUCTIONS Use black ink. You may use an HB pencil for graphs and diagrams. Complete the boxes above with your name, centre number and candidate number. Answer all the questions. Write your answer to each question in the space provided. Additional paper may be used if required but you must clearly show your candidate number, centre number and question number(s). INFORMATION The total mark for this paper is 60. The marks for each question are shown in brackets [ ]. Quality of extended responses will be assessed in questions marked with an asterisk (*). This document consists of 16 pages. Any blank pages are indicated. DC (SC/SG) /2 OCR is an exempt Charity Turn over

2 2 SECTION A Answer all the questions. You should spend a maximum of 20 minutes on this section. 1 Which description is correct for the particles in a gas? Arrangement Motion A Random Vibrating B Random Fast C Regular Vibrating D Regular Fast 2 Which property increases from one element to the next in the periodic table? A B C D Atomic number Mass number Number of neutrons Relative atomic mass 3 Which of the following elements is in both Period 2 and Group 3? A B C D Aluminium Beryllium Boron Magnesium

3 3 4 Phosphorus is in Group 5 of the periodic table. What is the charge on an ion of phosphorus? A P 2 B P 3 C P 4 D P 5 5 Solid iodine is heated until it changes state. Which type of forces or bonds are broken? A B C D Covalent Intermolecular Ionic Metallic 6 Nitrogen gas reacts with hydrogen gas to make ammonia gas, NH 3. Which equation is correct? A N(g) + 3H(g) NH 3 (g) B N(g) + H 3 (g) NH 3 (g) C 2N(g) + 3H 2 (g) 2NH 3 (g) D N 2 (g) + 3H 2 (g) 2NH 3 (g) Turn over

4 7 A calcium ion is Ca A nitrate ion is NO 3. What is the formula of calcium nitrate? A CaNO 3 B Ca 2 NO 3 C Ca(NO 3 ) 2 D Ca 2 (NO 3 ) 3 8 A chromatogram is shown below. Solvent front x y z Base line Which fraction gives the R f value of the spot? A B C D x y y x y z z y

5 5 9 What is the relative formula mass of Al (OH) 3? Use the periodic table to help you. A 40.0 B 46.0 C 78.0 D What is the percentage, by mass, of N in NH 4 NO 3? Use the periodic table to help you. A 16.7 B 17.5 C 33.3 D 35.0 Turn over

6 6 SECTION B Answer all the questions. 11 This question is about the element sodium. (a) The atomic number of sodium is 11. Different atoms of sodium can have different mass numbers. (i) Complete the table for sodium atoms with different mass numbers. Atomic number Mass number Protons Neutrons Electrons [3] (ii) Which word describes atoms of the same element with different mass numbers?... (b) The electrons in sodium atoms have the arrangement: (i) Explain how relates to sodium s position in the periodic table.... (ii) Sodium forms an ionic compound with the formula NaF. Construct a dot and cross diagram for NaF. Show outer electrons only and the charges on each ion. [2]

7 7 12 A student wants to make magnesium sulfate, MgSO 4. The student adds magnesium carbonate, MgCO 3 to sulfuric acid, H 2 SO 4. (a) The reaction makes carbon dioxide gas. Describe a test for carbon dioxide [2] (b) The equation for the experiment is shown below. MgCO 3 (s) + H 2 SO 4 (aq) MgSO 4 (aq) + CO 2 (g) + H 2 O(l) The student used an excess of magnesium carbonate. After doing the experiment, the reaction mixture contains magnesium sulfate solution and solid magnesium carbonate. (i) Explain how you could separate the magnesium sulfate solution from the solid magnesium carbonate. Include a labelled diagram of the apparatus. Diagram: Explanation:... [3] (ii) Explain how you could obtain pure magnesium sulfate from the magnesium sulfate solution.... [2] Turn over

8 13 Magnesium reacts with hydrochloric acid, HCl. The equation is shown below. 8 Mg(s) + 2HCl (aq) MgCl 2 (aq) + H 2 (g) A student investigates this reaction. Gas syringe Conical flask The student weighs some magnesium and adds it to the conical flask. He adds 50 cm 3 of hydrochloric acid to the flask and quickly replaces the bung. He records the final volume of gas in the syringe. The student repeats the experiment using different masses of magnesium. Look at the table of the student s results. Mass of Mg (mg) Volume of hydrogen (cm 3 )

9 (a) (i) Plot the results on the grid provided. 9 Volume H 2 (cm 3 ) Mass of Mg (mg) [3] Turn over

10 (ii) Which point is anomalous? 10 Explain how you can tell from your graph. Anomalous point... Explanation [2] (iii) Draw two straight lines of best fit: One line when the volume increases. One line when the volume stays the same. [2] (iv) Estimate the minimum mass of Mg, in mg, that reacts with all the acid. Use your two lines from (iii) to help you. Show your working on the graph. Answer =... mg [2] (b) When the student did his experiment, the cylinder in the syringe jammed. The student modified his experiment to obtain all the readings. Suggest how the student could modify the experiment using different apparatus available in a school laboratory [3]

11 (c) The student is given an unknown metal X. 11 The metal X reacts with hydrochloric acid to make hydrogen gas X(s) + 2HCl (aq) XCl 2 (aq) + H 2 (g) The student does an experiment to identify the unknown metal. The student adds the metal X to hydrochloric acid and measures the volume of gas 121 mg of the metal made 72.0 cm 3 of hydrogen gas. The relative atomic mass of the metal can be calculated using the equation below. mass in mg volume of hydrogen in cm3 = relative atomic mass 24.0 (i) Calculate the relative atomic mass of the metal X. Give your answer to 3 significant figures. (ii) Identify the unknown metal X. Use the periodic table to help you. Answer =... [3] Unknown metal X =... Turn over

12 12 14 A student does some experiments with acids, alkalis and salts. (a) The student mixes solutions of an acid and an alkali. The temperature increases. The reaction forms a salt and water, as shown below. alkali + acid salt + water (i) Name this type of chemical reaction.... (ii) The student concludes that the reaction is exothermic. Explain her conclusion.... [2] (b) In the student s experiment in (a), the student reacts the alkali KOH with the acid H 2 SO 4 to form the salt K 2 SO 4 and water H 2 O. (i) Construct a balanced symbol equation for the reaction [2] (ii) Name the alkali that the student used....

13 (c) The student adds a solution of the salt sodium chloride, NaCl, to a beaker. 13 The student sets up the circuit below using inert electrodes. d.c. supply + Cathode Anode Sodium chloride solution The student observes gas bubbles from each electrode. Sodium chloride solution contains these particles: Na + Cl H 2 O H + OH Predict the gas observed at each electrode. Gas at cathode ( ):... Gas at anode (+)... [2] Turn over

14 14 15 This question is about properties of carbon and aluminium. (a) Ethylene glycol is a carbon compound used in antifreeze. The displayed formula of a molecule of ethylene glycol is shown below. H H H O C C O H H H Each line represents a covalent bond. (i) Calculate the relative molecular mass of ethylene glycol.... (ii) What is the empirical formula of ethylene glycol?... (b) Carbon atoms form four covalent bonds. (i) Explain what is meant by a covalent bond in terms of electrons.... [2] (ii) Why can a carbon atom form four covalent bonds?...

15 (iii) 15 An organic compound in the same family as ethylene glycol has the molecular formula C 3 H 8 O 2. Draw a displayed formula for this molecule. (c) Diamond and graphite are crystalline forms of carbon. The table shows properties of diamond, graphite and aluminium. Substance Melting point ( C) Electrical conductivity Diamond 3550 Poor Graphite 3652 Very good Aluminium 2467 Very good Explain the properties of the substances in the table. Use the data from the table and your knowledge of structure and bonding [6] END OF QUESTION PAPER

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