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Find (a) the total number and (b) the total mass of protons in 34 mg of NH3 at STP.Will the answer change if the temperature and pressure are changed? |
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Answer» Mass of NH3 = 34 mg = 34 x 10-3 g Molar mass of NH3 = 17 g/mol Amount of ammonia = {34 x 10-3 g}/{17 g/mol} = 2 x 10-3 mol Therefore, No. of NH3 molecules in 34 mg sample = 2 x 10-3 mol x 6.023 x 1023 mol-1 = 1.2046 x 1021 Each molecule of NH3 contains 10 protons (7 protons in N+ 3 in three H atoms). Therefore, (a) No. of protons in 34 mg of ammonia = 10 x 1.2046 x 1021 = 1.2046 x 1022 (b) Mass of proton = 1.675 x 10-27 kg Therefore, total mass of protons in 34 mg of NH3 = 1.2046 x 1022 x 1.675 x 10-27 kg = 2.015 x 10-5 kg The number of neutrons, protons, molecules and mass does not depend upon temperature and pressure. Therefore there will be no change in the answers, if temperature and pressure are changed. |
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