Empirical Formula and Gas Law Homework
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Percent Composition Practice
1. What is the % composition by mass of ethanol, C2H5OH? 52.14%C, 13.13%H, 34.73%O
2. Calculate the percent composition of R-134a, C2H2F4. 23.54%C, 1.976%H, 74.48%F
Empirical Formula Practice
1. What is the empirical formula for a sample which contains 11.66g iron and 5.01g oxygen? Fe2O3
2. A 6.14 g sample of a compound of sulfur and oxygen is found to contain 2.46g of sulfur. What is the
empirical formula of the compound? SO3
3. What is the empirical formula for a sample found to be 40.0%C, 6.7%H, 53.3%O by mass? CH2O
4. Cadaverine, as its name suggests, is formed when bacteria digest dead meat. It is 58.77%C, 13.81%H, and
27.42%N. What is its empirical formula? C5H14N2
5. 10.0g of a hydrate of iron(III) nitrate is heated until all the waters of hydration are lost and 5.99g of
anhydrous salt remain. What is the formula of the hydrate? Fe(NO3)3∙9H2O
Molecular Formula Practice
1. Styrene, the monomer used to make polystyrene contains 92.3% C by mass and 7.7%H by mass and has a
molar mass of 104g/mol. What is its molecular formula? C8H8
2. The compound vanillin, the primary flavor compound in vanilla extract contains 63.15% C, 5.30% H, and
31.55% O, and has a molar mass around 152g/mol. What is the molecular formula of vanillin? C8H8O3
3. Eugenol is the primary component of clove oil. It contains 73.14% C, 7.367% H, and 19.49% O and has a
molar mass of 164g/mol. What is the molecular formula? C10H12O2
4. Limonene is a compound found in most citrus and contributes to their smell. It is 88.16% C and 11.84%
H with a molar mass around 136 g/mol. What is its molecular formula? C10H16
Gas Laws Practice #1
1. A 50.0L cylinder of argon gas at 19.8 atm has a temperature of 19.0°C. What volume of air could it
displace in a room at 0.974atm pressure at the same temperature? 1050L
2. A 1.0L balloon at 98.5kPa and 25°C is cooled to -196°C with liquid nitrogen at constant pressure. What is
the new volume of the balloon? 0.26L
3. What is the pressure in kilopascals inside a 20.0L container filled with 8.9mol of hydrogen gas at 25°C?
1100kPa (make sure you used the value of R with kPA in it!)
4. The maximum safe pressure that a certain 4.00 L container can withstand is 3.50 atm. If the container is
filled with 0.410 mol of gas, then what is the maximum temperature in Celsius that the container can
withstand? 143°C
5. How many moles of nitrogen are in a cylinder with a volume of 3.20L and a pressure of 15500 mmHg at
25.0°C? 0.26mol N2
Gas Law Practice #2
1. A 250mL balloon at 99.4kPa is placed in a container attached to a vacuum pump. The volume of the
balloon swells to 1.45L once the pump is turned on. What is the pressure inside the container? 17kPa
2. A particular reaction will generate 0.106mol of hydrogen gas at 25.0°C and 0.981atm. What volume will
the hydrogen occupy in mL? 2.64L
3. Liquid nitrogen is produced by forcing pressurized nitrogen through a tiny opening. The pressure drop
across the opening drops the temperature from room temperature (25.0°C) to at least the boiling point of
nitrogen (-196°C). If the nitrogen is expelled into 1.00 atm of pressure, what must be the pressure on the
other side of the opening to produce liquid nitrogen? Assume a constant volume process. 3.87atm
4. Show that at STP, one mole of gas has a volume of 22.4L. Use STP in the ideal gas equation.
5. A bacterial culture isolated from raw sewage produced 41.3mL of methane at 31°C and 750 mmHg. What
is the volume at STP? 37mL