**Instructions for Working out the Worksheets:**

Work in groups of 4 on these problems. You should try to answer the questions without referring to your textbook. If you get stuck, try asking another group for help. Your TA will come around when needed to help guide you if needed.

Round Robin Instructions:

- Each group member will be assigned a number, starting with #1 and ending with the number of people in the group.
- Student #1 will read the question aloud and define the information needed to solve the problem, create an outline on how you can solve the problem.
- When the group agrees that the necessary information is complete, student number two will do the first mathematical step. When the group agrees that the step is correct, student number three will do the next step. Continue this way until the group agrees that the given answer had been correctly converted to the wanted answer.
- Student #2 will start the next question by reading it aloud as in #1. Follow this pattern for all the questions in the session.

**Topics being Covered in the Worksheet:**

- Gas Laws 2. Go Over Exam 3

1-23 You will be solving the Gas Laws for the following problems to help better understand topic 1.The finding’s of 19th century chemists and physicists, among them Avogadro’, Gay-Lussac, Boyle, and Charles, are summarized in the **Ideal Gas Law:**

**PV = nRT**

**P = **pressure **V** = volume **n** = moles** R**= universal gas constant **T** = Temperature

The value of ** R** varies with the units chosen:

**R** = 0.08206 L•atm / mol•K **R** = 8.31 L•kPa / mol•K

In all cases, the **temperature must be expressed in K**, degrees kelvin.

- To standardize results, chemists often use set of experimental conditions, called
**standard temperature and pressure (STP)**.- Standard pressure = ________ atm = ________ torr = ________ mm Hg
- Standard temperature = ________ ºC = ________ K
- What is the standard molar volume of an ideal gas?

There are many types of Gas Law problem, but they can generally be groupound into two main types:

**Predicting the properties of a system**– One variable will be unknown, but the other three are known, and no changes occur. For these problem, use**PV = nRT.**The units must be liters, atmospheres, moles, and absolute temperature (K), since these are the units of**R**.**Changing conditions**– A change in any on e of the four variables, will lead to changes in the others. There will be a set of**initial conditions**and a set of**final conditions**.

Since R is a constant, this can be re-written as: | and |
PiVi R = Pf Vf = niTi nf Tf |

where **i** means initial state and **f** means final state

- When 1.10 g of magnesium reacted with 300.0 mL of 0.800 M HCl, the products where hydrogen gas and magnesium chloride. What volume of hydrogen gas would be collected if the reaction had been run at STP?
- Write the balance chemical equation
- Determine if there is a limiting reagent
- Determine the moles of hydrogen gas produced
- Determine the volume of the hydrogen gas at STP
- The reaction was actually carried out at room temperature, 25.0 ºC. What was the volume of hydrogen gas produced under these conditions?

- A gas that occupies a volume of 6.75 L at 89.0 atm will occupy what volume at 68.66 mmHg if the temperature remains constant?
- Which equation will allow you to solve for the missing information?
- What information do you know?

P | P |

V | V |

T | T |

n | n |

- Solve for the final volume.

- A 500.0 L sample of gas was collected at 20.0 ºC and 720.0 mm Hg. What is its volume at STP?

a)Which equation will allow you to solve for the missing information?

- What information do you know?

P | P |

V | V |

T | T |

n | n |

- Solve for the final volume.

- Which volume of O
_{2}gas, measured at 24 ºC, is needed to completely burn all of the methane (CH_{4}) in a 3.00 L container at the same T and P?

The Ideal Gas Law can bet re-arranged to calculate the molar mass of unknown gases.

PV = nRT n = mass (g) molar mass (g/mol)

PV = mass (RT) mass x R x T = molar mass molar mass P x V

Knowing that the units for **density** are **mass/volume, **re-write this equation so that is equates **density** with **molar mass**.

- Using the equation, derived above, determine the density of CO
_{2}at 745 mm Hg and 65 ºC? - A sample of gas of mass 2.929 g occupies a volume of 426 mL at 0 ºC and 1.00 atm pressure. What is the molecular weight of the gas?
- An unknown gas has a density of 3.167 g/L at STP. What is the identity of the gas? (Ar, O
_{2}, Cl_{2}, HF, or H_{2}O) - 0.30 g of a gas occupies a volume of 82.0 mL at 3.00 atm pressure and 27 ºC. Calculate the molar mass of the gas.
- Calculate the density of SF
_{6}at STP. - If I have 4 moles of gas at a pressure of 5.6 atm and a volume of 12 liters, what is the temperature?
- If I have an unknown quantity of gas at a pressure of 1.2 atm, a volume of 31 liters, and a temperature of 87 ºC, how many moles of gas do I have?
- If I contain 3 moles of gas in a container with a volume of 60 liters and at a temperature of 400. K, what is the pressure inside the container?
- If I have 7.7 moles of gas at a pressure of 0.09 atm and at a temperature of 56 ºC , what is the volume of the container that the gas is in?
- If I have 17 moles of gas at a temperature of 67 ºC, and a volume of 88.89 liters, what is the pressure of the gas?
- If I have ann unknown quantity of gas at a pressure of 0.5 atm, a volume of 25 liters, and a temperature of 300. K, how many moles of gas do I have?
- If I have 21 moles of gas held at a pressure of 78 atm and a temperature of 900. K, what is the volume of the gas?
- If I have 1.9 moles of gas held at a pressure of 5.0 atm and in a container with a volume of 50. liters, what is the temperature of the gas?
- If I have 2.4 moles of gas held at a temperature of 97 ºC and in a container with a volume of 45 liters, what is the pressure of the gas?
- If I have an unknown quantity of gas held at a temperature of 1195 K in a container with a volume of 25 liters and a pressure of 560. atm, how many moles of gas do I have?
- Calcium carbonate decomposes at high temperature to form carbon dioxide and calcium oxide:

CaCO_{3} *(s)* → CO_{2} *(g)* + CaO *(s)*

How many grams of calcium carbonate will I need to form 3.45 liters of carbon dioxide at STP?

- Ethylene burns in oxygen to form carbon dioxide and water vapor:

C_{2}H_{4} *(g)* + 3 O_{2} *(g)* → 2 CO_{2} *(g)* + 2 H_{2}O* (g)*

How many liters of water can be formed if 1.25 liters of ethylene are consumed in this reaction at STP?

- When chlorine is added to acetylene, 1,1,2,2-tetrachloroethane is formed:

2 Cl_{2} *(g)* + C_{2}H_{2} *(g)* → C_{2}H_{2}Cl_{4} *(l)*

How many liters of chlorine will be needed to make 75.0 grams of C_{2}H_{2}Cl_{4 }at STP?