It is called the atomic number. (In physics it can also be called the proton number)
Answer:
27) Double replacement
28) 2NaOH + H2SO4 --> Na2SO4 + 2H2O
Answer:
24.5%
Explanation:
You just add up the atomic masses.
Ca - 40.078
Cl2 - 35.4527 x 2 = 70.9054
------ 110.9834
H4 - 1.00794 x 4 = 4.03176
O2 - 31.9998
------ 36.03056
TOTAL - 147.01396
So the water is 36.03056/147.01396 = .245082576 but that is only accurate to three decimals (because the mass of Ca was only given to three decimals) so we write .245 and that is 24.5%
This is not my answer but I found it on Yahoo answers and it was answered by Anonymous.
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