What is the name of the solid that will form from the following reaction: a solution of hydrofluoric (HF) acid poured over barium carbonate crystals.

Which statement accurately describes the relationship between air pressure, air density, or altitude? as altitude increases, pressure increases.as altitude increases, air density increases.air pressure and density are lowest at sea level.denser air exerts more pressure than less dense air.

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

18. use the activity series to predict whether the following synthesis reaction will occur. write the chemical equations for the reaction if it's predicted to occur. (s) + o2(g) -> *note: it is possible.*