How was this equation derived?? Marshmallow #34

[ZainAlrawi_1J]

Lyndon sees his crush and panics, accidentally dropping 382.7 mg of HCl and 147.1 mg CaO into a 1L flask. After filling that flask with water up to the 1L mark, what is the pH of the resulting solution?

How do you go about deriving the equation HCl + Cao --> CaCl2 + H2O from this starting to point? Would really appreciate a step by step to how this problem is solved.

[Rory Simpson 2F]

The reaction between HCl and CaO would be a neutralization reaction between an acid and base that results in the formation of a salt and water. The balanced reaction would be 2HCl + CaO -> CaCl2 + H2O. Basically once you have the equation you want to find out how much of either HCl or CaO is leftover (since if one of them is limiting, then the other would be in excess and would cause the solution to change pH from neutral). Use the molar mass and the given mass values to find the moles of each and then find how many moles of one of the reactants are excess, then use that to find pH :)