Which of the following statements is true?

Radioactive cobalt-60 is frequently used in treating cancer. It took 24 years for a 10 gram sample to decay to 0.625 grams. What

-BARSIC- [3]

Answer:

Half life is 6 years.

Explanation:

T½ = In2 / λ

Where λ = decay constant.

But N = No * e^-λt

Where N = final mass after a certain period of time

No = initial mass

T = time

N = 0.625g

No = 10g

t = 24 years

N = No* e^-λt

N / No = e^-λt

λ = -( 1 / t) In N / No (inverse of e is In. Check logarithmic rules)

λ = -(1 / 24) * In (0.625/10)

λ = -0.04167 * In(0.0625)

λ = -0.04167 * (-2.77)

λ = 0.1154

T½ = In2 / λ

T½ = 0.693 / 0.1154

T½ = 6.00 years.

The half life of radioactive cobalt-60 is 6 years

5 0

3 years ago

Express the van der Waals equation of state as a virial expansion in powers of 1/Vm and obtain expressions for B and C in terms

nirvana33 [79]

Answer:

$PV_{m} = RT[1 + (b-\frac{a}{RT})\frac{1}{V_{m} } + \frac{b^{2} }{V^{2} _{m} } + ...]$

B = b -a/RT

C = b^2

a = 1.263 atm*L^2/mol^2

b = 0.03464 L/mol

Explanation:

In the given question, we need to express the van der Waals equation of state as a virial expansion in powers of 1/Vm and obtain expressions for B and C in terms of the parameters a and b. Therefore:

Using the van deer Waals equation of state:

$P = \frac{RT}{V_{m}-b } - \frac{a}{V_{m} ^{2} }$

With further simplification, we have:

$P = RT[\frac{1}{V_{m}-b } - \frac{a}{RTV_{m} ^{2} }]$

Then, we have:

$P = \frac{RT}{V_{m} } [\frac{1}{1-\frac{b}{V_{m} } } - \frac{a}{RTV_{m} }]$

Therefore,

$PV_{m} = RT[(1-\frac{b}{V_{m} }) ^{-1} - \frac{a}{RTV_{m} }]$

Using the expansion:

$(1-x)^{-1} = 1 + x + x^{2} + ....$

Therefore,

$PV_{m} = RT[1+\frac{b}{V_{m} }+\frac{b^{2} }{V_{m} ^{2} } + ... -\frac{a}{RTV_{m} }]$

Thus:

$PV_{m} = RT[1 + (b-\frac{a}{RT})\frac{1}{V_{m} } + \frac{b^{2} }{V^{2} _{m} } + ...]$ equation (1)

Using the virial equation of state:

$P = RT[\frac{1}{V_{m} }+ \frac{B}{V_{m} ^{2}}+\frac{C}{V_{m} ^{3} }+ ...]$

Thus:

$PV_{m} = RT[1+ \frac{B}{V_{m} }+ \frac{C}{V_{m} ^{2} } + ...]$ equation (2)

Comparing equations (1) and (2), we have:

B = b -a/RT

C = b^2

Using the measurements on argon gave B = −21.7 cm3 mol−1 and C = 1200 cm6 mol−2 for the virial coefficients at 273 K.

$b = \sqrt{C} = \sqrt{1200} = 34.64[tex]cm^{3}/mol$ [/tex] = 0.03464 L/mol

a = (b-B)*RT = (34.64+21.7)*(1L/1000cm^3)*(0.0821)*(273) = 1.263 atm*L^2/mol^2

3 0

3 years ago

2. Calculate the mass of 5.35 mole of H2O2.

Dmitry_Shevchenko [17]

Answer:

5.35m H2O2 x 34.02g/1m H2O2 = 182g H2O2

Explanation:

6 0

3 years ago

In the background, you were given the reactions for the fermentation of glucose to ethanol in the production of wine from grapes

ikadub [295]

Answer:

Kombucha is a Symbiotic culture of bacteria and yeast (SCOBY), similar to mother of vinegar, containing one or more specie each of bacteria and yeast which is added to sweet tea, which jump start two processes take place. First, alcoholic fermentation during which the yeast convert sugars to alcohol under controlled conditions. After that, the bacteria converts most of this alcohol into acetic, gluconic and glucoronic and other organic acids. during both of this processes, the yeast and bacteria, feast and multiply, yielding an end beverage that is rich in variety of micro organisms and healthy acids. Source: Health-Ade.com/blog/blog/what-is-fermentation

the products formed is more rich than those of the fermentation of grapes because it is a symbiotic fermentation of yeast and bacteria

Explanation:

Kombucha is fermented slightly alcoholic, lightly effervescent sweetend black or green tea, commonly consumed for its health benefits sometimes the beverage is called kombucha tea to distinguish it from the cultures of bacteria and yeast. Kombucha is thought to have originated in manchuria where the drink is traditionally consumed or in Russia and Eastern Europe.

Source: "A mug Of Kombucha for your health?" .<em>mayo clinic. </em>Retrieved 2018-09-01

7 0

3 years ago

Specific gravity of a vegetable oil is 0.85. What is its density?

elena-s [515]

I think its density is 850kg/m^3

6 0

2 years ago