Chapter 8
A mole is a unit of measure equal to 6.022x10^23, which is called Avogadro's number. One mole of any substance contains 6.022x10^23 units.
Atomic Mass Unit-amu
1 amu=1.66x10^-24g
One mole of an element has a mass equal to the element's atomic mass expressed in grams. The molar mass of any compound is the mass (in grams) of 1 mole of the compound and is the sum of the masses of the component atoms.
Percent composition consists of the mass percent of each element in a compound.
The empirical formula of a compound is the simplest whole-number ration of the atoms present in the compound; it can be derived from the percent composition of the compound. The molecular formula is the exact formula of the molecules present; it is always an integer multiple of the empirical formula.
Calculations
You have 20.4 mL of O2 gas. Find the number of molecules for the compound.
5.48x10^20 molecules of O2
Find the molar mass of H2O
18.0148g/1mol
You have 10.09 g of Neon. How many atoms are there?
3.011x10^23 atoms of Neon
Find the molar mass of N2H4
32.0456g/1mol
There are 6.022x10^23 atoms of aluminum. How many grams of aluminum are there?
26.98g of aluminum
How many g are in 2.69x10^-2 mol of mercury (I) chloride?
12.7g of mercury (I) chloride
Give the percent composition for BaO.
O=10.44% Ba=89.56%
A compound was analyzed and was found to contain the following percentages of the elements by mass: boron, 78.14%; hydrogen, 21.86%. Determine the empirical formula.
BH3
A compound with the empirical formula C2H5O was found in a separate experiment to have a molar mass of approximately 90g. What is the molecular formula of the compound?
C4H10O2
Atomic Mass Unit-amu
1 amu=1.66x10^-24g
One mole of an element has a mass equal to the element's atomic mass expressed in grams. The molar mass of any compound is the mass (in grams) of 1 mole of the compound and is the sum of the masses of the component atoms.
Percent composition consists of the mass percent of each element in a compound.
The empirical formula of a compound is the simplest whole-number ration of the atoms present in the compound; it can be derived from the percent composition of the compound. The molecular formula is the exact formula of the molecules present; it is always an integer multiple of the empirical formula.
Calculations
You have 20.4 mL of O2 gas. Find the number of molecules for the compound.
5.48x10^20 molecules of O2
Find the molar mass of H2O
18.0148g/1mol
You have 10.09 g of Neon. How many atoms are there?
3.011x10^23 atoms of Neon
Find the molar mass of N2H4
32.0456g/1mol
There are 6.022x10^23 atoms of aluminum. How many grams of aluminum are there?
26.98g of aluminum
How many g are in 2.69x10^-2 mol of mercury (I) chloride?
12.7g of mercury (I) chloride
Give the percent composition for BaO.
O=10.44% Ba=89.56%
A compound was analyzed and was found to contain the following percentages of the elements by mass: boron, 78.14%; hydrogen, 21.86%. Determine the empirical formula.
BH3
A compound with the empirical formula C2H5O was found in a separate experiment to have a molar mass of approximately 90g. What is the molecular formula of the compound?
C4H10O2
Activities:
Videos:
This is a video about moles and how it applies to this chapter.
This video explains and shows how to convert moles to grams.