If a 1.5 V AAA alkaline battery can power a 1.4 Watt device for 1 hour, how many grams of zinc (65.38g/mol) does it contain?
Overall reaction in battery: MnO_{2} + 2H_{2}O + Zn --> Mn(OH)_{2}+ ZnO
The answer is 1.1 g
Please explain step by step and how to reach this answer.
The equation
P = I*V
then
I = P/V
P = 1.4 watt; V = 1.5
then
I = 1.4/1.5 = 0.9333 Amp
1 amp = 1 C/s = 0.9333 C/s
t = 3600 s so
0.9333*3600 = 3359.88 C
convert to mol of electrons
1 mol of e- = 96500 C
then
3359.88/96500 = 0.0348174 mol of electrons being transferred
MnO2 + 2H2O + Zn --> Mn(OH)2+ ZnO
Zn goes from 0 to +2 therefore
2 mol of e are being transferred
for every mol of Zn
0.0348174/2 --> 0.0174087mol of Zn
mass of Zn = mol*MW = 0.0174087*65.38 = 1.138180806 g of Zn
If a 1.5 V AAA alkaline battery can power a 1.4 Watt device for 1 hour,...
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