2021_YIJC_Prelim_P1_Ans

©YIJC [Turn Over YISHUN INNOVA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 1 CANDIDATE NAME CG INDEX NO H1 GROUP CHEMISTRY Paper 1 Multiple Choice Additional Materials: Multiple Choice Answer Sheet Data Booklet 8873/01 16 September 2021 1 hour READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, highlighters, glue or correction fluid/tape. Write your name and class on the Answer Sheet in the spaces provided unless this has been done for you. There are thirty questions on this paper. Answer all questions. For each question there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate Answer Sheet. Read the instructions on the Answer Sheet very carefully. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. The use of an approved scientific calculator is expected, where appropriate. This document consists of 11 printed pages and 1 blank pages.

2 @YIJC [Turn Over 1 10 cm3 of a hydrocarbon CxHy was exploded with an excess of oxygen. There was a contraction of 30 cm 3. When the product was treated with a solution of potassium hydroxide, there was a further contraction of 40 cm3. What is the molecular formula of the hydrocarbon? [All gas volumes are measured at r.t.p.] A C4H8 B C4H10 C C3H6 D C3H8 [volume of hydrocarbon + volume of O2] – [volume of CO2 + volume of O2 remaining] = 30 10 + volume of O2 – [40 + volume of O2 remaining] = 30 volume of O2 – volume of O2 remaining = 60 volume of O2(reacted) = 60 cm3 CxHy + (x + y 4)O2(g)  xCO2 +( y 2)H2O CxHy : O2 CO2 : H2O stoichiometric ratio from balanced equation 1 mol (x + y 4) x mol volume ratio 10 cm3 60 cm3 40 cm3 1 cm3 6 cm3 4 cm3 mole ratio 1 mol 6 4 mol 2 Three organic molecules each have • three elements; • the composition, by mass, C, 54.5 %; H, 9.1 %. What could these molecules be? 1 CH3CH2CH2CO2H 2 OHCCH2CH2CH2OH 3 CH3CH=CHCH2SH A 1, 2 and 3 B 1 and 2 C 2 and 3 D 1 and 3 Suppose the 3rd element is O : C H O Mass in 100g 54.5 9.1 36.4 No. of moles 54.5  12.0 = 4.54 9.1  1.0 = 9.1 36.4  16.0 = 2.275 Ratio 2 4 1 Empirical formula : C2H4O Suppose the 3rd element is S : C H S

3 @YIJC [Turn Ov