The vapor pressure of water changes with temperature, as shown here. A student d
ID: 516232 • Letter: T
Question
The vapor pressure of water changes with temperature, as shown here.
A student designs an ammeter (a device that measures electrical current) that is based on the electrolysis of water into hydrogen and oxygen gases. When electrical current of unknown magnitude is run through the device for 4.00 min , 16.9 mL of water-saturated H2(g) is collected. The temperature and pressure of the system are 25 C and 715 torr.
T (C) P (torr) 21 18.7 22 19.8 23 21.1 24 22.4 25 23.8 26 25.2 27 26.7 28 28.4 29 30.0 30 31.8Explanation / Answer
A student designs an ammeter (a device that measures electrical current) that is based on the electrolysis of water into hydrogen and oxygen gases. When electrical current of unknown magnitude is run through the device for 4.00 min , 16.9 mL of water-saturated H2(g) is collected. The temperature and pressure of the system are 25 ?C and 715 torr
n = PV / RT = (715 torr - 23.8 torr) × (0.0135 L) / ((62.36367 L?torr/K?mol) × (25 + 273) K)
= 5.021 × 10^-4 mol H2
2 H{+} + 2 e{-} ? H2
=(5.021 × 10^-4 mol H2) × (2 mol e{-} / 1 mol H2) × (9.64853399 × 10^4 C/mol e{-}) / (3.50 min × (60 sec/min)) =
=0.461 amperes
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