<em><u>Answer</u></em><em><u> </u></em>: HBr polar
<em><u>please</u></em><em><u> </u></em><em><u>add</u></em><em><u> </u></em><em><u>me</u></em><em><u> </u></em><em><u>to</u></em><em><u> </u></em><em><u>brainalist</u></em>
The redox reaction is

Here
Calcium undergoes reduction, and acts as cathode
Lithium undergoes oxidation and acts as anode
The reduction potential of calcium is -2.87 V
The reduction potential of lithium is - -3.05 V
We know that
Ecell = Ecathode - Eanode
Ecell = -2.87 - (-3.05) = 0.18 V
Answer:
The filter bed is cleaned by occasional backwashing ;-; im sorry if this isn't a great answer but I tried
1 mole ------------- 6.02x10²³ atoms
4.93 moles ------- ??
4.93 x ( 6.02x10²³) / 1 =
=> 2.96x10²⁴ atoms