Consider the diffusion of oxygen through a low-density polyethylene (LDPE) sheet 15 mm thick. The pressures of oxygen at the two faces are 2000 kPa and 150 kPa, which are maintained constant. Assuming conditions of steady state, what is the diffusion flux [in $\left.\left(\mathrm{cm}^{3} \mathrm{STP}\right) / \mathrm{cm}^{2} \cdot \mathrm{s}\right]$ at 298 K?

Write each number in scientific notation. 0.00725

Change the following word equations into formula equations. Methane $\left(\mathrm{CH}_4\right)$ reacts with oxygen gas to form carbon dioxide and water.

When the viola section of an orchestra with six members plays together, is the sound 6 times as loud as when a single viola plays? Explain. Is the intensity 6 times what it would be for a single viola? [Hint: The six sound waves are not coherent.]

A bouquet of 40 flowers is made up of roses, carnations, and daisies. The bouquet is 45% roses and 15% carnations. How many of the flowers are roses? carnations?

Solve the inequality. Graph your solution. -7r > 49

The following table lists molecular weight data for a polytetrafluoroethylene material. Compute the following:

(a) the number-average molecular weight

(b) the weight-average molecular weight

(c) the degree of polymerization

$$\begin{matrix}\text{Molecular Weight}\\\text{Range (g/mol)} & \mathrm{x_{i}} & \mathrm{w_{i}}\\\text{10,000-20,000} & \text{0.03} & \text{0.01}\\\text{20,000-30,000} & \text{0.09} & \text{0.04}\\\text{30,000-40,000} & \text{0.15} & \text{0.11}\\\text{40,000-50,000} & \text{0.25} & \text{0.23}\\\text{50,000-60,000} & \text{0.22} & \text{0.24}\\\text{60,000-70,000} & \text{0.14} & \text{0.18}\\\text{70,000-80,000} & \text{0.08} & \text{0.12}\\ \text{80,000-90,000} & \text{0.04} & \text{0.07}\\\end{matrix}$$

Given the reaction $\mathrm { A } ( g ) + \mathrm { B } ( g ) \rightleftharpoons \mathrm { C } ( g ) + \mathrm { D } ( g ) ,$ consider the following situations: i. You have 1.3 M A and 0.8 M B initially. ii. You have 1.3 M A, 0.8 M B, and 0.2 M C initially. iii. You have 2.0 M A and 0.8 M B initially. After equilibrium has been reached, order i-iii in terms of increasing equilibrium concentrations of D. Explain your sequence. Then give the order in terms of increasing equilibrium concentration of Band explain.

Determine the ratio of butadiene to acrylonitrile repeat units in a copolymer having a number-average molecular weight of 250,000 g/mol and a degree of polymerization of 4640.

(a) Compute the repeat unit molecular weight of polypropylene.

(b) Compute the number-average molecular weight for a polypropylene for which the degree of polymerization is 15,000.

Describe how the Law of Cosines can be used to solve the ambiguous case of the oblique triangle ABC, where a=12 feet, b=30 feet, and A = 20° Is the result the same as when the Law of Sines is used to solve the triangle? Describe the advantages and the disadvantages of each method.

The density and associated percent crystallinity for two poly(ethylene terephthalate) materials are as follows: $$ \begin{matrix}\mathrm{\rho\left(g / c m^{3}\right)} & \text{crystallinity (\\%)}\\\text{1.408} & \text{74.3}\\\text{1.343} & \text{31.2}\\\end{matrix} $$ (a) Compute the densities of totally crystalline and totally amorphous poly(ethylene terephthalate). (b) Determine the percent crystallinity of a specimen having a density of $1.382 \mathrm{g} / \mathrm{cm}^{3}$.

determine the null and alternative hypotheses. The standard deviation in the pressure required to open a certain valve is known to be $\sigma$=0.7 psi. Due to changes in the manufacturing process, the quality-control manager feels that the pressure variability has been reduced.

The number-average molecular weight of a polystyrene is 500,000 g/mol. Compute the degree of polymerization.