Chapter 5
Activity 6 – Ideal Gas Law for the Ideal Toy
What Do You See? – page 401What Do You Think? – page 401
How does a toy company know how many times a CO2 cartridge can be used to shoot the darts in a dart gun before it runs out?
Investigate
1. Your teacher measured the mass of 100 cm of polished magnesium ribbon. Record this mass in the data table below.
2. Get a small piece of magnesium ribbon from your teacher. Carefully measure its length to the nearest 0.05 cm. Record the length of your piece of magnesium in the data table below.
Mass of 100 cm of Mg ribbonLength of small piece of Mg ribbon
Mass of small piece of Mg ribbon
Moles of Mg in small piece of ribbon
3. Use the information in the data table above to calculate the mass of your small piece of magnesium ribbon in grams.
4. Convert the mass in grams of magnesium ribbon to moles of magnesium. (This is a plus sign problem). Remember, 1 mole of any element is equal to its atomic mass in grams. Record your answer in the data table above.
5. Turn to page 402 in your textbook. Follow the directions in your textbook to complete the lab activity. The directions start in the middle of the first column on page 402.
6. Record the data you collected in the table below.
Air pressure in the roomVolume of gas in the gas-collecting tube
7. Clean up your lab station. Put the liquid from the gas collecting tube and the water in your beaker in the waste bucket on the front counter. Return all supplies to the front counter.
8. The equation for the reaction you did in lab today is shown below:
Mg (s) + 2HCl (aq) → H2 (g) + MgCl2 (aq)
The balanced equation shows that 1 mole of magnesium reacts with two moles of hydrochloric acid (HCl) to make 1 mole of magnesium chloride (MgCl2).
a) The balanced equation also shows that 1 mole of magnesium (Mg) will produce 1 mole of hydrogen gas (H2). The number of moles of magnesium you used is equal to the number of moles of hydrogen gas that forms. Record the number of moles of hydrogen gas produced in the table below.
Moles of Mg used in reactionMoles of H2 made in reaction
b) You recorded the volume in milliliters (mL) of hydrogen gas collected during your experiment. Change milliliters to liters. Show your work below. Remember, 1 L = 1000 mL.
c) Now, calculate the volume of 1 mole of hydrogen gas. Show your work below. This is the number of liters in a mole of hydrogen gas at the temperature and pressure in our classroom.
______L of H2 = ______L______mol of H2 mol
9. You have learned about the relationship between temperature, pressure, and volume of a gas in earlier activities. These relationships can be expressed using the Combined Gas Law.
P1 V1 = P2 V2
T1 T2
You will use this equation to calculate the molar volume of a gas at standard temperature (0OC) and standard pressure (1 atm or 760 mm Hg). These conditions are called STP.
a) Record the room temperature and pressure provided by your teacher.
b) Change the temperature in Celsius to temperature in Kelvin by adding 273. Record your answer in the data table below.
In Your Lab / At STPP / 760 mm Hg
V
T / 273 K
c) Use the Combined Gas Law equation to calculate the volume of 1 mole of hydrogen gas at STP. Record your answer in the data table.
P2T1
P1 =
V1 =
T1 =
P2 = 760 mm Hg
T2 = 273 K
d) Scientists have done an experiment similar to the experiment you did in class today. These experiments have shown that, at STP, the volume of any gas is 22.4 mol/L. How close was your value?
e) What are some factors that might account for the difference between your value and the accepted value?
10. You now can write a mathematical formula to tell the relationship between the pressure, volume, temperature, and amount of gas in moles.
PV = constant P= pressure, V=Volume, T=temperature, n=moles of gas
Tn
Using the conditions at STP, calculate the constant, R, which is called the Ideal Gas Constant.
(1 atm) (22.4 L) = R
(273 K) (1 mole)
R =
ChemTalk – page 404 – 405
Checking Up – pg. 405
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Chem To Go – pg. 407
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