<span>all the ones that phase down are exothermic - freezing, deposition, condensation.
all the ones that phase up are endothermic - melting, sublimation, vaporization
endothermic is to gain heat, exothermic is to release heat</span>
Answer:
15.7g
Explanation:
mass percent=mass of element/mass of compound *100
39.34=unknown(x)/40g×100
39.34=5x/2
multiplying both sides by 2,we get
5x=78.68
devide by 5 on both sides
x=15.74g Na