Transcript Chapter 3 Review Questions


What is the percent composition of
Ca(OH)2?
54.09% Ca, 43.18% O, 2.73% H

What is needed to calculate the average
atomic masses of elements?
Percent abundances of all isotopes and
the atomic mass of each isotope

How many moles are in 2.50 x 1023
formula units of NaBr?
0.415mol NaBr

After dividing all mole values by the
smallest mole value to obtain the
empirical formula for a compound, a
student ended up with the following: 1.5
O atoms, 2 H atoms, and 1.5 S atoms.
What is the correct empirical formula?
O3H4S3

If the molecular formula of a compound
is C6H18O6, what is the empirical formula?
CH3O

What is the molecular formula given that
the empirical formula is CH and the
experimental molar mass is 78g/mol?
C6H6

Which has a greater mass- 1mol Mg or
1mol Sr?
1mol Sr
Why aren’t molar masses on the periodic
table whole numbers?
Because a weighted average of all
isotopes’ masses are used.

What is the average atomic mass of
silicon given the following isotopes:
92.21% has a mass of 27.98amu, 4.70%
has a mass of 28.98amu, and 3.09% has
a mass of 29.97amu.
28.09 amu

What is the empirical formula if the
percentage composition of a compound
is 60.0% carbon, 13.4% hydrogen, and
26.6% oxygen?
C3H8O