NYGH 2022-S3EOY-IP Chem P2

Class Register Number Name End-of-Year Examination 2022 Secondary 3 IP CHEMISTRY Paper 2 1 hour 45 minutes Wednesday 5 October 1030 – 1215 READ THESE INSTRUCTIONS FIRST Write your name, register number and class in the spaces at the top of this page. Write in dark blue or black pen. You may use a pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid / tape. Section A Answer all questions in the spaces provided. You are advised to spend no longer than 1 hour on Section A, and no longer than 45 minutes on Section B. The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table is on page 11. The use of an approved scientific calculator is expected, where appropriate. Section A (40 marks) Section B (30 marks) Total (70 marks) This document consists of 10 printed pages and 2 blank pages. Setter(s): OWJ/CHG NANYANG GIRLS' HIGH SCHOOL [Turn over A

2 Setters: OWJ/CHG Chemistry Paper 2 Section A (40 marks) Answer all questions. Write your answers in the spaces provided. A1 Epsom salt is a bitter-tasting salt with the chemical formula, MgSO 4.nH2O. It is widely used as bathing salt to relieve body aches. (a) (i) Suggest the chemical formulae of two suitable reactants for making aqueous magnesium sulfate, stating which one is in excess. [2] (ii) State how the excess reactant can be removed from aqueous magnesium sulfate. [1] (iii) State the most suitable method by which Epsom salt can be obtained from aqueous magnesium sulfate. [1] (b) A sample of Epsom s alt weighing 4.93 g initially was strongly heated in an evaporating dish until it decomposed to form the anhydrous salt, MgSO4. The following graph was obtained. (i) State the minimum temperature required to decompose the Epsom salt into the anhydrous salt. [1] oC (ii) Calculate the relative molecular mass of anhydrous magnesium sulfate, MgSO4. [1] mass of solid / g temperature / oC 4.93 2.41 250 65

3 Setters: OWJ/CHG Chemistry Paper 2 [Turn Over (iii) Calculate the number of moles of MgSO4.nH2O in 4.93 g of Epsom Salt. [1] (iv) Using the information in the graph and answer in (b)(iii), derive the exact chemical formula of Epsom salt, showing all necessary working. [3] Total [10]

4 Setters: OWJ/CHG Chemistry Paper 2 A2 A sample of X contains three substances, A, B and C. (a) In an experiment, a student conducting the experiment accidentally dripped a drop of sample X into the solvent. The student observed that the colour of sample X spread through the solvent. Name this phenomenon, and explain why the phenomenon occur. [2] (b) The retention factor (R f) values of substances A, B and C in the respective solvents are given in the table below. A B C water 0.20 0.20 0.60 ethanol 0.80 0.40 0.40 Another experiment is carried out on the sample X using two-dimension (2D) paper chromatography. The following steps show how 2D paper chromatography is carried out to separate the substances in X: 1. Separate the sample using water. 2. Rotate the paper 90 degrees clockwise. 3. Carry out further separation on the sample using ethanol as solvent. (i) Use the information in the table to explain why it is necessary to use 2D paper chromatography. [2]

5 Setters: OWJ/CHG Chemistry Paper 2 [Turn Over (ii) In the 2D paper chromatography that was done , the distance of the solvent front from the start line when water and ethanol are used as solvents are both 10 cm. In the paper chromatogram shown below, each point on the scale represents 1 cm. The position of substance A is shown in the paper chromatogram. On the paper chromatogram, draw the location of the spots for substances B and C, and label them accordingly. [2] Start line 1 and solvent front 1: water is used as a solvent. Start line 2 and solvent front 2: ethanol is used as a solvent. The point marked as X is the initial position of sample X. Total [6] start line 1 start line 2 solvent (water) front 1 solvent (ethanol) front 2 A

6 Setters: OWJ/CHG Chemistry Paper 2 A3 Borospherene, B40, is a new molecule discovered in 2014. The structure of borospherene is shown below. (a) In terms of its structure, explain why borospherene is expected to have poor electrical conductivity. [2] (b) State and explain whether borospherene is expected to have a high or low boiling point. [2] (c) Predict and explain whether the boiling point of borospherene is expected to be higher or lower than that of methane, CH4. [2] (d) By considering the number of valence electrons that boron has, explain why the bonding between boron atoms in borospherene is unusual. [1] Total [7]

7 Setters: OWJ/CHG Chemistry Paper 2 [Turn Over A4 A new element Z was discovered and found to have the following properties.  melting point of 25 °C  conducts electricity in solid and liquid state  reacts violently with water and hydrochloric acid (a) (i) Identify the Group that element Z is in. [1] (ii) Other than the properties given, state another physical property that element Z is expected to have. [1] (b) (i) Write a chemical equation , with state symbols , for the reaction between element Z and water. [2] (ii) Element Z is an element below Period 6 in the Periodic Table. By considering the trend in the tendency of elements to lose electrons down the Group, explain why element Z is very reactive. [3] (iii) Element X is an element one period above Z in the Periodic Table. Element Y contains one more proton than element X. By considering how the tendency of the elements to lose electrons changes across the Period and down the Group, ar range the elements in order of the most reactive to the least reactive. [1] Total [8]

8 Setters: OWJ/CHG Chemistry Paper 2 A5 The atmosphere of a n unknown planet was analysed and it was found to contain nitrogen, carbon dioxide , oxygen and argon. The following set -up was used to determine the volume of oxygen in the planet’s atmosphere. Fig. 1 The oxygen present in the sample of air reacts with copper solid to form copper(II) oxide, a black solid. 2Cu(s) + O2(g)  2CuO(s) The volume of air used for the experiment was originally 80.0 cm3 while the original mass of copper used was 2.50 g. After the experiment, the unreacted copper was separated from the copper(II) oxide formed by dissolving the copper(II) oxide in excess dilute nitric acid. The mixture was filtered to obtain a filtrate while the unreacted copper residue was washed, dried and weighed to be 2.25 g. (a) (i) Calculate the number of moles of copper reacted with oxygen. [1] (ii) Calculate the volume of oxygen reacted, expressing the answer in cm3. [1] (iii) Calculate the percentage of oxygen present in the planet’s atmosphere. [1] gas syringe containing the sample of air from the unknown planet copper solid

9 Setters: OWJ/