Name ____________________________________________________________ Period ____________
Chapter 10: The Mole
Keller/Rosenzweig
Mole Conversions with Compounds
Once the molar mass of a compound is calculated, it can be used for mole conversions in the same way as
atomic mass, using the conversion factors. Use the example below as a guide if needed.
Example: Convert 2.45g of chromium (III) cyanide to moles
STEP 1: Write the correct formula. Since chromium (III) cyanide is ionic, charges will need to be crossed.
Cr+3
CN-1 = Cr(CN)3
STEP 2: Find the molar mass:
1 atom Cr (52.0g/mol) + 3 atoms C (12.0g/mol) + 3 atoms N (14.0g/mol) = 130.0g Cr(CN)3
1 mol Cr(CN)3
STEP 3: Use the molar mass for dimensional analysis:
2.45g Cr(CN)3
1 mol Cr(CN)3 = 0.018885 mol Cr(CN)3
130.0g Cr(CN)3
STEP 4: Go back to the original problem to determine the number of significant figures to include in the
answer.
2.45g = 3 significant digits;
ANSWER: 0.0189 mole Cr(CN)3
PRATICE PROBLEMS:
1.
Find the mass of 0.655 moles of potassium phosphate.
potassium hydroxide: _______________________
2.
How many moles are in 35.0g of aluminum hydroxide?
aluminum hydroxide: _______________________
3.
Find the mass of 1.25 moles of trisilicon tetranitride.
trisilicon tetranitride: ________________________
4. How many molecules are in 14.0g of pentacarbon decahydride?
pentacarbon decahydride: __________________
5. Find the mass of 2.25 x 1022 formula units of magnesium cyanide.
magnesium cyanide: ____________________
6. How many molecules are in 14.0g of hydronitric acid?
hydronitric acid: _____________
7. How many molecules are in 25.3g of carbon dioxide?
carbon dioxide: ____________