Ask question

Ask question

All categories

3 years ago

7

Given a sample of poly[ethylene-stat-(vinyl acetate)] A.Calculate the mean repeat unit molar mass for a sample of poly[ethylene-

stat-(vinyl acetate)] that comprises 12.9 wt% vinyl acetate repeat units.B.Given that its number-average molar mass is 39,870 g/mol, calculate the number-average degree of polymerization of the copolymer.

1 answer:

AlladinOne [14]3 years ago

5 0

Answer:

a) The mean repeat unit molar mass for PEVA is 30.72 g/mol

b) degree of polymerization of the copolymer is 1300

Explanation:

Given that;

the wt% of copolymer consist of 12.9 wt% of vinyl acetate and 87.1 wt% Ethylene.

Basis: 100 g of PEVA consist of 12.9 of vinyl acetate and 87.1g of Ethylene.

now we calculate the mole fraction of vinyl acetate Ethylene in the copolymer;

the molecular weights of vinyl acetate and ethylene are 86.09 g/mol and 28.05 g/mol respectively

so

moles of vinyl acetate = wt. of vinyl acetate / molecular weights of vinyl acetate

moles of vinyl acetate = 12.9 g / 86.09 g/mol

moles of vinyl acetate = 0.1498 mol

moles of Ethylene = wt. of Ethylene / molecular weights of Ethylene

moles of Ethylene = 87.1 g / 28.05 d/mol

moles of Ethylene = 3.1052 mol

Total moles = 0.1498 mol + 3.1052 mol = 3.255 mol

Next we calculate the mole percent;

mole percent of vinyl acetate $X_{V}$ = moles of vinyl acetate / total moles

$X_{V}$ = (0.1498 mol / 3.255 mol) × 100

$X_{V}$ = 4.6%

mole percent of Ethylene $X_{E}$ = moles of Ethylene / total moles

$X_{E}$ = (3.1052 mol / 3.255 mol) × 100

$X_{E}$ = 95.397% ≈ 95.4%

we know that, mean repeat unit molar mass for a sample = ∑ $X_{i}$ $M_{i}$

where $X_{i}$ is the fraction ratio and $M_{i}$ is the molecular weight

so or the PEVA

mean repeat unit molar mass M = ( $X_{V}$ $M_{V}$ ) + ( $X_{E}$ $M_{E}$ )

so we substitute

M = ( 4.6% × 86.09) + ( 95.4% × 28.05 )

M = 3.96014 + 26.7597

M = 30.72 g/mol

Therefore, The mean repeat unit molar mass for PEVA is 30.72 g/mol

b)

Degree of polymerization

$DP_{n}$ = $\frac{M_{n} }{M}$

where $M_{n}$ is the number average molecular weight ( 39,870 g/mol )

so we substitute

$DP_{n}$ = 39,870 g/mol / 30.72 g/mol

$DP_{n}$ = 1297.85 ≈ 1300 { 3 significance figure }

Therefore, degree of polymerization of the copolymer is 1300

You might be interested in

A student claims that if she wanted to make a solution quickly, she should use small pellets instead of powder along with heatin

vova2212 [387]

Answer: Yes we agree with the student's claim.

Explanation:

When the molecules are present in smaller size, more reactants can react as decreasing the size increases the surface area of the reactants which will enhance the contact of molecules.Hence, more products will form leading to increased rate of reaction.

On increasing the temperature will make more reactant molecules will have sufficient energies to cross the energy barrier and thus the number of effective collisions increases, thus leading to more products and increased rate of reaction.

When the solution is stirred , the molecule's kinetic energy and thus the rate of reaction increases.

Thus smaller size, stirring and increase of temperature will make the solution quickly.

7 0

4 years ago

Which colorless and odorless gas, produced by radioactive decay of Uranium-238, is considered to be a cancer-causing agent?

DiKsa [7]

B, radon is correct. Interestingly, it often collects in basements from radioactive decay of rocks such as granite that contain uranium. Because it is an unreactive noble gas and because it is denser than air it sits in basements and must be pumped out. It collects in human lungs and is the second leading cause of lung cancer behind smoking.

7 0

3 years ago

Four physical properties of 500g of butter

Sergeu [11.5K]

A piece of paper is thin, slightly smooth, can be white and smell woody. 500 g of butter has a density of 0.911 g/ml and has a volume thus of 548.85 ml.

5 0

3 years ago

CADMIUM SOLUBILITY AND pH Cadmium is a toxic metal. It can be removed from water by chemical precipitation of solid cadmium hydr

Serga [27]

Explanation:

It is known that,

Molar mass of Cd = 112.41 g/mol

Standard concentration of Cd = 0.005 mg/L = $0.005 \times 10^{-3}$ g/L

Hence, we will calculate the molarity as follows.

Molarity = $\frac{0.005 \times 10^{-3}}{112.41} mol/L$

= $4.45 \times 10^{-8}$ M

Equation for the reaction is as follows.

$Cd(OH)_{2} \rightleftharpoons Cd^{2+} + 2OH^{-}$

$K_{sp} = [Cd^{2+}][OH^{-}]^{2}]$

$2 \times 10^{-34} = 4.45 \times 10^{-8} \times [OH^{-}]^{2}$

$[OH^{-}] = 6.7 \times 10^{-4}$ M

Also,

$[H^{+}] = \frac{10^{-14}}{[OH^{-}]}$

= $\frac{10^{-14}}{6.7 \times 10^{-4}}$

= $1.49 \times 10^{-11} M$

Relation between pH and concentration of hydrogen ions is as follows.

pH = $-log [H^{+}]$

= $-log (1.49 \times 10^{-11} M)$

= 10.82

Thus, we can conclude that a minimum pH of 10.82 is necessary to reduce the dissolved cadmium ion concentration to the standard.

4 0

3 years ago

A bacterium called Bacillus thuringiensis (B.t.) contains a protein that can kill cotton ballworms and certain other kinds of ca

olga2289 [7]

This is genetic engineering.

I hope this helps!

Cheer,s July.

3 0

4 years ago

Read 2 more answers