Module 6

Lesson 3.1  Calculating Charge (Q)



Key Concepts



To quantify the number of electrons transferred in a cell, first calculate the charge that has passed through the electrochemical cell. Charge is symbolized by "Q" and measured in Coulombs. It can be calculated by multiplying current (amperes) by time (seconds).

\({ Q = It } \)

For example, calculate the charge transferred by a current of 1.5 A (amperes) flowing for 30 seconds.

\( Q = \mathrm{1.5 \frac{C}{s} \times 30 s } \) 


\(   Q = \mathrm {45C } \)

Read pages 652-654  in your textbook, Nelson Chemistry.  Carefully work through the Sample problems and Communication examples on these pages.

Check Your Understanding


Complete Practice Questions 2,3, and 4 on page 653 of your textbook. Click the link below to check your work.

Page 653 Practice Question 2 

\( \mathrm { I = Q/t } \)

\( \mathrm { = \dfrac{87.6~ C}{22.5~ s} = 3.89 \frac{C}{s} } \)

The electric current is 3.89 C/s.

Page 653 Practice Question 3

\( \mathrm { Q = It } \)
\( \mathrm { = (250 \times 10^{-3}~ \frac{C}{s})(28.5 s) } \)
\( \mathrm { = 7.13 C } \)

The charge transferred is 7.13 C.

Page 653 Practice Question 4

\( \mathrm { t = Q/I } \)

\( \mathrm { = \dfrac{375~ C}{1.60~ \frac{C}{s}} = 234~ s } \)

\( \mathrm { = (234~ s) \times \dfrac{1~ min}{60~ s} = 3.91~ min } \)

The time taken is 3.91 min.