What is the coefficient for potassium in the balanced equation: Na +
K2S -->
K +
Na2S

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.

i believe the answer is 5,000