Write one effect of gravitational force of the sun and the moon on the earth.​

Can someone me with questions 12 and 13 plz.

Silver tarnishes as silver metal reacts with hydrogen sulfide, h2s, in the air. in this reaction, dark silver sulfide, au2s, covers the surface of silver. when silver is polished, this coating of silver sulfide can be removed from the surface. this makes the silver shiny again. enter the coefficients that balance the tarnishing reaction equation. (type 1 for no coefficient.)

What forms when chemical reactions combine pollution with sunlight?