paper 3chem july 2017 mkg schm.docx - Nameu2026Marking...

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Name… Marking Scheme Index No…………………/……. School……………………………………………………… Date ……………… Candidate’s Signature………… 233/3 CHEMISTRY Paper 3 JULY 2017 Time: 2 ¼ Hours 3G JOINT EVALUATION TEST– 2017 Kenya Certificate of Secondary Education (K.C.S.E) INSTRUCTIONS TO CANDIDATES 1. Write your name and index number in the spaces provided above. 2. Sign and write the date of the examination in space provided. 3. Answer ALL the questions in the spaces provided in the question paper. 4. All working MUST be clearly shown where necessary. 5. Mathematical tables and silent electronic calculators may be used. 6. This paper consists of 6 printed pages. Candidates should confirm this. FOR EXAMINER’S USE ONLY This paper consists of 6 printed pages. 1. You are provided with: Magnesium ribbon, solid A 1 QUESTION MAXIMUM SCORE CANDIDATE’S SCORE 1 24 2 8 3 8 TOTAL SCORE 40
0.7M hydrochloric acid, solution B 0.3M sodium hydroxide, solution C Distilled water You are required to determine the: (i) the temperature change when magnesium reacts with excess hydrochloric acid (ii) number of moles of hydrochloric acid that remained unreacted (iii) number of moles of magnesium that reacted (iv) molar heat of reaction between hydrochloric acid and magnesium Procedure 1 Using a burette, measure 50cm 3 of solution B and place it in a 100ml beaker. Measure the temperature of solution B and record the value in table 1. Put the magnesium ribbon in the 50cm 3 of solution B in the 100ml beaker, and immediately start a stop clock/stop watch. Stir the mixture completely with the thermometer making sure he magnesium ribbon remains inside the solution

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