HONORS STUDY GUIDE: MOLES TEST
Vocabulary:
Moles- 6.02 x 1023 of anything is equal to 1 mole. A counting unit.
Representative Particles- can stand for atoms, moles, formula units, etc.
Avagadro’s number- 6.02 x 1023
Percent composition- the percent by mass of each element in a compound.
Empirical Formula- the simplest form of an equation. The lowest whole number ratio.
Molecular Formula- the actual number of atoms in a formula. Not reduced.
Hydrate- Ionic compound with water molecules trapped in it.
Anhydrous- Compound that does not contain water molecules.
Mole Conversions:
1. How many moles are in 28.6g of CH2?
2.04 moles
2. What is the mass of 3.2 moles of H2O?
57.66 g
3. How many formula units are in 2.8 x 1021 moles of C6H12O6?
1.68 x 1045 F.U.
4. How many moles are in 6.8 x 10-21 atoms of Carbon?
1.13 x 10-44 moles
5. How many particles are in 24.3 g of Sodium chloride?
2.50 x 1023 particles
6. What is the mass of 5.8 x 1016 molecules of Mg3(PO4)2?
2.53 x 10-5 g
Percent Composition:
1. What is the percent compostion of calcium chloride?
CaCl2
Ca: 36.11%
Cl: 63.89%
2. Which has a higher percent by mass of Oxygen: H2SO3 or H2PO4?
H2PO4
Empirical Formulas:
1. Determine the empirical formula for a compound that is composed of 35.98% aluminum and 64.02%
sulfur.
Al2S3
2. A compound is composed of 65.98g Ba, 24.32g O, and 6.09g C. Find the empirical formula of the
compound.
BaCO3
Molecular Formulas:
1. Which of the following formulas- NO, N2O, NO2, N2O4, and N2O5- represent the empirical and
molecular formulas of the same compound? Explain your answer
2. The chemical analysis of Vitamin D is as follows: 84.31% Carbon, 11.53% Hydrogen, and 4.16%
Oxygen. Determine the molecular formula of Vitamin D if the sample size is 770g
C27H44O –Empirical
C54H88O2 -Molecular
Hydrates:
1. Why are certain electronic devices transported with dessicants?
Dessicants are anhydrous compounds. They can absorb water to become hydrates. This will keep the
electronics from being ruined by any moisture.
2. Chromium (III) nitrate forms a hydrate that is 40.50% water by mass. What is its chemical formula?
Cr(NO3)3 ∙ 9H2O
3. What is the formula and name of a hydrate that is 85.3% barium chloride and 14.7% water?
BaCl2 ∙ 2 H20
4.
5.
Name the following compounds:
a)
FeCl3. 6 H2O ___Iron (III) chloride hexahydrate_______________
b)
CuSO4 . 5 H2O _____Copper (II) sulfate pentahydrate____________
Write the formulas for the following compounds:
a)
barium chloride dihydrate ____BaCl2 ∙ 2H2O_____________________________
b)
magnesium sulfate heptahydrate MgSO4 ∙ 7H2O