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Elements of Crystallizes in Body-Centered Cubic Lattice

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Chapter 11

5. An element crystallizes in a body-centered cubic lattice. The edge of the unit cell is 2.98 , and the density of the crystal is 8.99 . Calculate the atomic weight of the element.

9. Calculate the minimum number of grams of propane, , that must be combusted to provide the energy necessary to convert 5.70 of ice at -18.0 to liquid water at 71.5 .

21. The vapor pressure of a volatile liquid can be determined by slowly bubbling a known volume of gas through it at a known temperature and pressure. In an experiment, 4.08 of gas is passed through 7.4972 of liquid benzene, , at 27.1 and atmospheric pressure. The liquid remaining after the experiment weighs 5.9261 . Assuming that the gas becomes saturated with benzene vapor and that the total gas volume and temperature remain constant, what is the vapor pressure of the benzene in torr?

Chapter 14

7. The activation energy of an uncatalyzed reaction is 91 . The addition of a catalyst lowers the activation energy to 52

A. Assuming that the collision factor remains the same, by what factor will the catalyst increase the rate of the reaction at 34 ?

B. Assuming that the collision factor remains the same, by what factor will the catalyst increase the rate of the reaction at 112 ?

12. Calculate the fraction of atoms in a sample of argon gas at 337 that have an energy of 12.3 or greater.

25. The decomposition of H2O2, H2O2 (aq)  H2O (l) + ½ O2 (g), is a first-order reaction. At a particular temperature near room temperature, the rate constant equals 7.0×10−4 . Calculate the half-life at this temperature.

34. At 415 , decomposes in the gas phase, . If the reaction is first order with a half-life of 56.3 at this temperature, calculate the rate constant in .

Chapter 20

11. A solution is electrolyzed, using a current of 8.00 .

A. What mass of is plated out after 3.00 days?
B. What amperage is required to plate out 0.230 from a solution in a period of 7.30 ?

23. How many coulombs are required to plate a layer of chromium metal 0.29 thick on an auto bumper with a total area of 0.30 from a solution containing ? The density of chromium metal is 7.20 .

28. What current flow is required for this electroplating if the bumper is to be plated in 14.2 ?

32. If the external source has an emf of 6.6 and the electrolytic cell is 69 efficient, how much electrical power is expended to electroplate the bumper?

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The elements of crystallizes in body-centered cubic lattice are determined.

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Chapter 11

5. An element crystallizes in a body-centered cubic lattice. The edge of the unit cell is 2.98 , and the density of the crystal is 8.99 . Calculate the atomic weight of the element.

Length of unit edge = 2.98 A x (1 x 10-8 cm/A) = 2.98 x 10-8 cm
Volume of unit cell = (2.98 x 10-8 cm)3 = 2.65 x 10-23 cm3

In body-centered cubic lattice, 2 atoms occupy a unit cell.

8.99 g/cm3 (2.65 x 10-23 cm3) = 2.38 x 10-22 g (mass of 2 atoms)

Mass of 1 atom = 2.38 x 10-22 g /2
Mass of 1 atom = 1.19 x 10-22 g

Atomic weight = 1.19 x 10-22 g/atom (6.022 x 1023 atoms/mole)

Atomic weight = 71.63 g/mol

9. Calculate the minimum number of grams of propane, , that must be combusted to provide the energy necessary to convert 5.70 of ice at -18.0 to liquid water at 71.5 .

To raise the temp of ice from -18 C to its melting point of O0C:
H = mCT
H = 5700 g (2.1J/g-C)(180C)
H = 215,460 Joules

To melt the ice:
H = mC
H = 5700 grams (333J/g)
H = 1,898,100 Joules

To raise the temp of liquid water from 0 C to 71.5 0C
H = mCdT
H = 5700 g (4.184J/g-C)( 71.5 0C)
H = 1,705,189.2 Joules

The sum of the 3 processes Htotal is:
Htotal = 3,818,749.2 Joules
Htotal = 3,818.75 kiloJoules

The heat of combustion of propane is 49.9 kJ/g
Therefore,
49.9 kJ /g propane = 3,818.75 kiloJoules/x

x = 76.53 g of propane

21. The vapor pressure of a volatile liquid can be determined by slowly bubbling a known volume of gas through it at a known temperature and pressure. In an experiment, 4.08 of gas is ...

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