Mountains into Molehills
Mass-Mole Conversions
Purpose: To practice converting from mass to moles and from moles to mass.
Part 1: Cyanide Compounds
Cyanide, CN-, is a toxic polyatomic ion found in many compounds. Four of these compounds are shown in the
table. Compare 2.5 grams of each cyanide compound to determine which is the most toxic.
Cyanide Compound
Chemical
Formula
NaCN
KCN
KAu(CN)2
Sodium cyanide
Potassium cyanide
Potassium gold
cyanide
Magnesium cyanide
Mg(CN)2
1. Complete Table 1 on Student worksheet.
a. Determine molar mass (grams per mole) from a periodic table for each compound. Express
molar mass values to the nearest tenth of a gram.
b. Determine the number of moles in 2.5 grams of each compound. Use the equality to set up a
conversion. Use unit analysis to calculate the value and correct unit for the answer.
c. Determine the number of cyanide ions (CN-) present in one formula unit of each compound.
d. Determine the number of moles of cyanide ions (CN-) in 2.5 grams of each compound.
Complete Table 2 by answering the following questions.
2. What charge does CN have in KCN and in Mg(CN)2? How do you know?
3. Explain how you determined the number of moles of CN ions in each compound?
4. Based on the number of moles of cyanide in each compound, place the four compounds in order from
most toxic to least toxic.
5. Explain why potassium gold cyanide has so few moles of cyanide compared to the other compounds.
6. Which has more moles of cyanide, 1g of NaCN or 1g of KCN?
Part 2: Vitamins
1. People often take vitamins to supplement their diet. Complete Table 3, converting moles to mass and
mass to moles for some common vitamins.
2. Which has more mass, 1 mole of vitamin A of 1 mole of vitamin C?
3. Which has more moles of carbon atoms, 169.2g of vitamin B6 or 176.1g of vitamin C?
Making sense:
1. Explain how to convert from mass in grams to number of moles.
2. How can you convert the number of moles of a substance to mass in grams?
If You Finish Early:
How many molecules of L-ascorbate are in 1000mg vitamin C tablet? (1mole = 6.02x1023 molecules)
Period:
Name:
Part 1: Cyanide Compounds
Table 1:
Cyanide
Compound
𝑮𝒐𝒂𝒍
Chemical
Formula
Molar
Mass
Sodium
cyanide
NaCN
48.0
g/mol
Potassium
cyanide
KCN
=
Potassium
gold
cyanide
KAu(CN)2
=
Magnesium
Mg(CN)2
cyanide
=
Table 2:
2
3
4
5
6
=
𝑮𝒊𝒗𝒆𝒏
Conversion
𝑥 𝑚𝑜𝑙
2.5𝑔
=
1 𝑚𝑜𝑙
49.0𝑔
Number of moles of the stated
compounds in 2.5g
2.5𝑔
× 1𝑚𝑜𝑙 = 0.051𝑚𝑜𝑙
49.0𝑔
Number of
CN ions in
1 formula
Number of
moles of CN
in 2.5g
1 CN ion
0.051mol
Part 2: Vitamins
Table 3:
Vitamin A, Retinol, C20H30O
Molar Mass = ___________g/mol
Milligrams
Grams
Moles
5000
1000
100
Vitamin B6, Pyridoxine, C8H11NO3
Molar Mass = ___________g/mol
Milligrams
Grams
Moles
1000
500
250
Show work for Vitamin ______, ___________mg
Molar mass
Grams
Vitamin C, L-ascorbate, C6H8O6
Molar Mass = ___________g/mol
Milligrams
Grams
Moles
20000
10000
5000
Moles
2
3
Making Sense
1. Use the _________________________ to determine the __________________________ of the compound.
_________ the molar masses of _______________________________ in the compound. Divide the
___________________ of the sample by the ________________________ to get the number of moles.
2. First, determine the molar mass of the substance from the ____________________________. Then,
If You Finish Early