The Mole and Chemical Composition (Chapter 7)

Question 1

Percent composition formula

Answer 1

(total mass of element in compound / molar mass of compound) x 100

Question 2

Average atomic mass formula

Answer 2

mass isotope 1 x decimal form of % of isotope 1 + mass isotope 2 x decimal form of % of isotope 2 + …

Question 3

What unit do you put after isotope masses in avg. atomic mass equations?

Answer 3

amu (atomic mass unit)

Question 4

Molar mass formula

Answer 4

Total mass element A + total mass element B + …

Question 5

What unit do you put after each element in molar mass formula?

Answer 5

g/mol

Question 6

What place are avg. atomic mass solutions rounded to?

Answer 6

Hundredths place

Question 7

Empirical formula solution steps

Answer 7

1) Percent –> grams
2) Mass –> moles
3) Divide by smallest number of moles
4) Multiply by 2 if #’s are super close to _.5
5) Round to whole #
6) Write formula

Question 8

Molecular formula solution steps

Answer 8

1) Find empirical formula
2) Find molar mass of empirical formula
3) find x: x = molecular formula mass / empirical formula mass
4) Multiply subscripts by x

Question 9

Mass vs molar mass

Answer 9

Mass: g
Molar mass: g/mol