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iogann1982 [59]
2 years ago
12

A sample contains 16. 75 g of the radioisotope U-236 and 50. 25 g of its daughter isotope, Th-232. How long did it take for deca

y to take place if one half-life of U-236 is 23 million years? 46 million years 69 million years 92 million years 115 million years.
Chemistry
2 answers:
garri49 [273]2 years ago
8 0

The time taken for the isotope to decay is 46 million years.

We'll begin by calculating the number of half-lives that has elapsed. This can be obtained as follow:

  • Original amount (N₀) = 50.25 g
  • Amount remaining (N) = 16.75
  • Number of half-lives (n) =?

2ⁿ = N₀ / N

2ⁿ = N₀ / N

2ⁿ = 50.25 / 16.75

2ⁿ = 3

Take the log of both side

Log 2ⁿ = 3

nLog 2 = Log 3

Divide both side by log 2

n = Log 3 / Log 2

n = 2

Finally, we shall determine the time.

  • Half-life (t½) = 23 million years
  • Number of half-lives (n) = 2
  • Time (t) =?

t = n × t½

t = 2  × 23

t = 46 million years

Learn more about half-life: brainly.com/question/25927447

nekit [7.7K]2 years ago
3 0

Answer:

A.46 Million years

Explanation:

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GREYUIT [131]

Based on Dalton's Law, for a mixture of gases, the total pressure is the sum of the partial pressure of each gas.

Partial pressure (p) of each gas is related to the total pressure (P) as follows:

p = X * P----------(1)

where X is the mole fraction of that gas

X = moles of a particular gas/total number of moles of all gases in the mixture--------------(2)

Step 1: Calculate the moles of each gas

Mass of methane, CH4 = 11 g

Mass of nitrogen, N2 = 1.4 g

Mass of carbon dioxide, CO2 = 16 g

# moles of CH4 = 11 g/16 gmol-1 = 0.6875

# moles of N2 = 1.4/28 = 0.05

# moles of CO2 = 16/44 = 0.3636

Total moles = 0.6875+0.05+0.3636 = 1.1011

Step2: Calculate mole fractions of each gas

Based on equation (2)

X(CH4) = 0.6875/1.1011 = 0.6244

X(N2) = 0.05/1.1011 = 0.0454

X(CO2) = 0.3636/1.1011 = 0.3302

Step 3: Calculate the total pressure

Based on ideal gas equation:

PV = nRT

given that;

V = 28 L

n = total moles = 1.1011

R = gas constant = 0.0821 Latm/mol-K

Since temp T is not given, let us consider room temperature of 25 C = 25 + 273 = 298 K

Now, P = nRT/V = 1.011*0.0821*298/28 = 0.962 atm

Step 3: Calculate partial pressures

Based on equation:

p(CH4) = 0.6244*0.962 atm = 0.601 atm

P(N2) = 0.0454*0.962 atm = 0.044 atm

P(CO2) = 0.3302*0.962 atm = 0.318 atm


4 0
3 years ago
Which set of quantum numbers cannot specify an orbital?.
vodomira [7]

Answer: n=2,l=1,ml=1 n=3,l=2,ml=0 n=3,l=3,ml=2 n=4,l=2,ml=0.

Explanation:

hope it helps

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2 years ago
True or False: If you have 2 moles of water and 2 moles of carbon, you have the same number of molecules.
nikklg [1K]
True.
moles x avagadro number = molecules
8 0
3 years ago
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The density of Mg is 1.74g/cm3. The density of strontium is 2.60g/cm3. What would you expect the density of Ca to be?
Tomtit [17]

The density of Ca will be between that of Mg and Sr

Explanation:

Ca, Mg and Sr are group II elements. They are called alkali earth metals. The correct order of the elements in this group are: Be, Mg, Ca, Sr, Ba and Ra.

Density is an intensive property of matter which describes the amount of matter(mass) per volume of a substance.

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  • On the periodic table, atomic mass which the number of protons and neutrons in the nucleus of an atom increases down the group.
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Learn more:

density brainly.com/question/2658982

mass number brainly.com/question/2597088

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6 0
3 years ago
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Georgia [21]

Answer:

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