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salantis [7]
3 years ago
14

After two half-lives, a sample contains 10 grams of parent isotopes. How many grams of the parent isotope were present to start?

Chemistry
2 answers:
Lunna [17]3 years ago
8 0
T=2T
m=10 g

m=m₀2^(-t/T)

m₀=m/{2^(-2T/T)=m/2⁻²

m₀=10/2⁻²=40 g

40 grams
almond37 [142]3 years ago
8 0
Theirs a total of 39.9999G at the start
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The molar mass of vitamin A (C20H30O).
vivado [14]
Molar mass of C:  12.011 g/mol
The equation says C20, which means there are 20 carbon atoms in each molecule of Vitamin A.  So, we multiply 12.011 by 20 to get 240.22 g/mol carbon.

Molar mass of H:  1.0079 g/mol
The equation says C30, which means there are 30 hydrogen atoms in each molecule of Vitamin A. So, we multiply 1.0079 by 30 to get 30.237 g/mol hydrogen.

Molar mass of O: 15.999 g/mol
The equation says O without a number, which means there is only one oxygen atom in each molecule of Vitamin A.  So, we leave O at 15.999 g/mol.

Then, just add it up:
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4 0
3 years ago
Mixtures of benzene and cyclohexane exhibit ideal behavior. A solution was created containing 1.5 moles of liquid benzene and 2.
goblinko [34]

Answer:

Vapour pressure of cyclohexane at 50°C is 490torr

Vapour pressure of benzene at 50°C is 90torr

Explanation:

Using Raoult's law, pressure of a solution is defined by the sum of the product sbetween mole fraction of both solvents and pressure of pure solvents.

P_{solution} = X_{A}P^0_{A}+X_{B}P^0_{B}

In the first solution:

X_{cyclohexane}=\frac{2.5mol}{2.5mol+1.5mol} =0.625

X_{benzene}=\frac{1.5mol}{2.5mol+1.5mol} =0.375

340torr = 0.625P^0_{A}+0.375P^0_{B} <em>(1)</em>

For the second equation:

X_{cyclohexane}=\frac{3.5mol}{3.5mol+1.5mol} =0.700

X_{benzene}=\frac{1.5mol}{3.5mol+1.5mol} =0.300

370torr = 0.700P^0_{A}+0.300P^0_{B}<em>(2)</em>

Replacing (2) in (1):

340torr = 0.625P^0_{A}+0.375(1233.3-2.333P^0_{A})

340torr = 0.625P^0_{A}+462.5-0.875P^0_{A}

-122.5torr = -0.250P°A

P^0_{A} = 490 torr

<em>Vapour pressure of cyclohexane at 50°C is 490torr</em>

And for benzene:

370torr = 0.700*490torr+0.300P^0_{B}

P^0_{B}=90torr

<em>Vapour pressure of benzene at 50°C is 90torr</em>

3 0
3 years ago
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Answer:

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