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Faraday. HIGHER GRADE CHEMISTRY CALCULATIONS. The quantity of electrical charge flowing in a circuit is related to the current and the time. Faraday. Where Q is the electrical charge in coulombs (C) I is the current in amps (A) t is the time in seconds (s).

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## Faraday

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**HIGHER GRADE CHEMISTRY CALCULATIONS**The quantity of electrical charge flowing in a circuit is related to the current and the time. Faraday Where Q is the electrical charge in coulombs (C) I is the current in amps (A) t is the time in seconds (s) Q = I x t Faradays law of electrolysis states that n x F coulombs of charge are required to deposit 1 mole of a substance. Where n is the number of electrons in the ion-electron equation and F is the Faraday (96 500C)**Faraday**Worked example 1. Calculate the mass of copper deposited when a current of 0.5 A is passed through copper(II) sulphate solution for 1 hour. Step 1:- Q = I x t = 0.5 x 60 x 60 = 1800 C Step 2:- Use the ion-electron equation to calculate the charge to give 1 mol. Cu2+(aq) + 2e- Cu(s) 2F 1 mole 2 x 96500 C 1 mole 193000 C 1 mole Step 3:- Calculate the mass deposited by number of coulombs in step 1. 193000 C 1 mole 193000 C 63.5 g So 1800 C 1800/193000 x 63.5 0.59 g Higher Grade Chemistry**Calculations for you to try.**• Calculate the mass of hydrogen formed when a current of 0.4 A is passed through hydrochloric acid solution for 3 hours. Q = I x t = 0.4 x 3 x 60 x 60 = 4320 C 2H+(aq) + 2e- H2(g) 2 F 1mol 2 x 96500 C 1 mol 193000 C 1 mol 19300 C 1 mol 2 g So 4320 C 4320/193000 x 2 0.045 g Higher Grade Chemistry**Calculations for you to try.**• Calculate the volume of chorine produced when a current of 2 A is passed though sodium chloride solution for 5 hours 40 minutes. • Take the molar volume of a gas to be 23.8 l mol-1. Q = I x t = 2 x 340 x 60 = 408 000 C (5 hours 40 minutes = 340 minutes) 2Cl-(aq) Cl2(g) + 2e- 1mol 2F 1 mol 2 x 96 500 C 1 mol 193 000 C 19300 C 1 mol 23.8 litres So 408 000 C 408 000/193000 x 23.8 50.31 litres Higher Grade Chemistry**Calculations for you to try.**3. Electrolysis of nickel(II) chloride solution produced 2.925 g of nickel per hour. What current was flowing? 58.5 g of nickel 1 mol So 2.925 g 2.925 /58.5 mol 0.05 mol Ni2+(aq) + 2e- Ni(s) 2 F 1mol 2 x 96500 C 1 mol 193000 C 1 mol 1 mol of nickel 193000 C So 0.05 mole 193 000 x 0.05 C 9650 C Q = I x t So I = Q/t I = 9650/60 x 60 = 2.68 A Higher Grade Chemistry**Q = I x t**= 2 x 40 x 60 = 4800 C Calculations for you to try. • A chromium compound was electrolysed using a current of 2A for • 40 minutes. The mass of chromium deposited was 0.864 g. • Calculate the charge on the chromium ion. 52.0 g of chromium 1 mol So 0.864 g 0.864 /52.0 mol 0.0166 mol 0.0166 mol of chromium 4800 C So 1 mole 1 /0.0166 x 4800 C 289156 C 96500 C 1 Farady So 289156 C 289156/96500 = 2.996 F The charge on the ion = 3+.

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