If a 40 g sample of NaCl is composed of 39.34% Sodium, how many grams of
that sample are Sodium?

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

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e

1. they vary with a higher number because boiling is way hotter than melting