Question

I need A and C

± Changes in Volume The ideal gas law (PV=nRT) describes the relationship among pressure P, volume V, temperature T, and molar amount n. When some of these variables are constant, the ideal gas law can be rearranged in different ways to take the following forms where k is a constant: Name Expression Constant Boyle's law PV=nRT=k n and T Charles's law VT=nRP=k n and P Avogadro's law Vn=RTP=k T and P

Part A A certain amount of chlorine gas was placed inside a cylinder with a movable piston at one end. The initial volume was 3.00 L and the initial pressure of chlorine was 1.65 atm . The piston was pushed down to change the volume to 1.00 L. Calculate the final pressure of the gas if the temperature and number of moles of chlorine remain constant.. (Figure 1) Express your answer with the appropriate units. Hints Pfinal= SubmitMy AnswersGive Up Part B In an air-conditioned room at 19.0 ∘C, a spherical balloon had the diameter of 50.0 cm. When taken outside on a hot summer day, the balloon expanded to 51.0 cm in diameter. What was the temperature outside in degrees Celsius? Assume that the balloon is a perfect sphere and that the pressure and number of moles of air molecules remains the same. Express your answer with the appropriate units. Hints outside temperature = 36.9 ∘C SubmitMy AnswersGive Up Correct Since, at a constant pressure, the volume of an ideal gas is directly proportional to its temperature, the plot of volume versus temperature is a straight line. When temperature is plotted on the Celsius scale, the straight line can be extrapolated to the point where the volume is zero and the temperature is −273 ∘C. Because matter cannot have a negative volume, −273 ∘Cmust be the lowest possible temperature, absolute zero. Significant Figures Feedback: Your answer 36.87∘C was either rounded differently or used a different number of significant figures than required for this part. Part C A cylinder with a movable piston contains 2.00 g of helium, He, at room temperature. More helium was added to the cylinder and the volume was adjusted so that the gas pressure remained the same. How many grams of helium were added to the cylinder if the volume was changed from 2.00 L to 2.50 L ? (The temperature was held constant.) Express your answer with the appropriate units. Hints mass of helium added = SubmitMy AnswersGive Up

Answer 1

Part A) A certain amount of chlorine gas was placed inside a cylinder with a movable piston at one end. The initial volume was 3.00 L and the initial pressure of chlorine was 1.65 atm . The piston was pushed down to change the volume to 1.00 L. Calculate the final pressure of the gas if the temperature and number of moles of chlorine remain constant.

V1 = 3L, P1 = 1.65 atm; V2 = 1L, P2 = ?

this is Boyle's law, T and n are constant so V*P = K (constant)

so

V1*P1 = V2*P2

solve for P2

V1 = 3L, P1 = 1.65 atm; V2 = 1L, P2 = ?

3L*1.65atm = 1L*P2

P2 = 3*1.65/1 = 4.95 atm

The new pressure is 4.95 atm, since the volume decreases

Part C)

A cylinder with a movable piston contains 2.00 g of helium, He, at room temperature. More helium was added to the cylinder and the volume was adjusted so that the gas pressure remained the same. How many grams of helium were added to the cylinder if the volume was changed from 2.00 L to 2.50 L ? (The temperature was held constant.)

m = 2 g of Helium, MW of He = 4 g/mol

mol = mass/MW = 2/4 = 0.5 mol of He

n1 = 0.5 mol of H2; V1 = 2L

n2 = ? V2 = 2.5 L

this is Avogrado's Law

so:

V1/n1 = V2/n2

substitute and solve for n2

n2 = V2/V1*n1

n2 = 2.5/2*0.5 = 0.625 mol of He

change in moles = 0.625 -0.5 = 0.125 mol of He were added

mass added = mol*MW = 0.125*4 = 0.5 g of He added