What is the bohr model for MgF2?

Can someone me with questions 15 to 17 plz.

Voltaic cells produce a positive overall charge. what does this indicate? a. the reaction is likely to be endothermic. b. the reaction is spontaneous. c. the reaction is not likely to occur. d. the reaction is not spontaneous.

In the experiment you asked to react hydrochloric acid and with sodium hydroxide. when measuring the volume of the reactants, which instrument would give the greatest precision.