Use the ideal gas law to calculate an unknown property. A sample of Kr gas has a

Question

Use the ideal gas law to calculate an unknown property. A sample of Kr gas has a volume of 723 mL, has a pressure of 447 mm Hg, and is at a temperature of 6.60 degree C. Calculate the amount (in moles) of Kr in the gas sample. Use Avogadro's law to calculate volume. A sample of gas contains 0.140 mol of C_2H_4(g) and 0.140 mol of Br_2(g) and occupies a volume of 9.62 L. The following reaction take place: C_2H_4(g) + Br_2(g) rightarrow CH_2BrCH_2Br(g) Calculate the volume of the sample after the reaction takes place (assume temperature and pressure are constant). L

Explanation / Answer

PV = nRT

where:

P is the pressure of the gas = 0.588 atm

V is the volume of the gas = 0.723 Liter

n is the amount of substance of gas (in moles)

R is gas constant = = 0.0821 L atm K-1 Mol-1

T is the absolute temperature of the gas = 273 + 6.6 = 279.6 K

Substitute the values and find n

n = PV /RT

n = 0.588 x 0.723 / 0.0821 x 279.6 = 0.01852 Moles

Question 2

Balanced equation:
C2H4 + Br2 ===> CH2BrCH2Br

After reaction 0.14 mole of product will be formed

Let us find the initial pressure

n = 0.14 + 0.14 = 0.28

V = 9.62 L

T = 273 K

P = 0.28 x 0.0821 x 273 / 9.62

P1 = 0.652 atm

Final pressure will be half of the amount in intial pressure since it produces 0.14 Mole product

P2 = 0.326

V1 = 9.62 L

P1V1 = P2V2

V2 = 0.652 x 9.62 / 0.326 = 19.24 Liter

Hence volume after reaction takes place is 19.24 Liter

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