How many milliliters of calcium, with a density of 1.55 g/ml, are needed to produce 76.4 grams of calcium fluoride in the single replacement reaction below? be sure to show the work that you did to solve this problem. unbalanced equation: ca + hf > caf2 + h2

First need to write balanced equation: Ca + 2 HF ---> CaF2 + H2 
Convert 76.4 g CaF2 into moles: MW = 1(40.078) + 2(18.998) = 78.074 g/mole Moles: (76.4 g)(1 mole / 78.074 g) = 0.9786 moles 
By stoichiometry: 1 mole Ca is needed for every mole of CaF2 produced So we need 0.9786 moles Convert this to mass: (0.9786 moles)(40.078 g/mole) = 39.22 g Ca needed 
(39.22 g)(1 mL / 1.55 g) = 25.3 mL 
We need 25.3 mL of Ca solution

I hope this helps!

Exothermic,  physical change after it is already baked