What must be true for a spontaneous reaction in an electrochemical cell? The overall cell potential must be positive. The overall cell potential must be negative. The cathode’s standard reduction potential must be positive. The cathode’s standard reduction potential must be negative.

The overall cell potential must be positive.

Explanation:

What must be true for a spontaneous reaction in an electrochemical cell?

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"

6.4 cm (max) - 25 cm (min)