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Dafna1 [17]
3 years ago
6

131i has a half-life of 8.04 days. assuming you start with a 1.53 mg sample of 131i, how many mg will remain after 13.0 days ___

_______?
a.0.835
b.0.268
c.0.422
d.0.440
e.0.499
Chemistry
1 answer:
inn [45]3 years ago
8 0
For this problem we can use half-life formula and radioactive decay formula.

Half-life formula,
t1/2 = ln 2 / λ

where, t1/2 is half-life and λ is radioactive decay constant.
t1/2 = 8.04 days

Hence,         
8.04 days    = ln 2 / λ                         
λ   = ln 2 / 8.04 days

Radioactive decay law,
Nt = No e∧(-λt)

where, Nt is amount of compound at t time, No is amount of compound at  t = 0 time, t is time taken to decay and λ is radioactive decay constant.

Nt = ?
No = 1.53 mg
λ   = ln 2 / 8.04 days = 0.693 / 8.04 days
t    = 13.0 days 

By substituting,
Nt = 1.53 mg e∧((-0.693/8.04 days) x 13.0 days))
Nt = 0.4989 mg = 0.0.499 mg

Hence, mass of remaining sample after 13.0 days = 0.499 mg

The answer is "e"

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A balloon inflated in a room at 24 degree celsius has a volume of 4 L. The balloon is then heated to a temperature of 58 degree
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Answer: The new volume of the balloon will be 4.45L

Explanation: We will solve this question through the concept of Charles's law. The law states that the volume of a gas is directly proportional to the absolute temperature, assuming the quantity of gas and pressure remain constant.

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2 years ago
b. Sugar and salt are both white, crystalline powders that dissolve in water. If you were given an unknown sample that contained
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Answer:

Explanation:

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Read more at Answer.Ya.Guru – https://answer.ya.guru/questions/4803546-sugar-and-salt-are-both-white-crystalline-powders-that-dissolve.html

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Consider the decomposition of red calx of mercury (HgO) into its elements as follows:
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2 years ago
How much energy in joules is released when 18.5 grams of copper cools from 285 °C<br> down to 45 °C
nadya68 [22]

Answer: 1709.4 Joules

Explanation:

The quantity of Heat Energy (Q) released on cooling a heated substance depends on its Mass (M), specific heat capacity (C) and change in temperature (Φ)

Thus, Q = MCΦ

Since Q = ?

M = 18.5 grams

Recall that the specific heat capacity of copper C = 0.385 J/g.C

Φ = 285°C - 45°C = 240°C

Then, Q = MCΦ

Q = 18.5grams x 0.385 J/g.C x 240°C

Q = 1709.4 Joules

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5 0
3 years ago
0.0145 moles of helium gas are introduced into a balloon so that the volume of the balloon is 2.54 liters. An additional amount
olga_2 [115]

Answer:

4.43L is final volume of the ballon

Explanation:

Avogadro's law of ideal gases states that <em>equal volumes of gases, at the same temperature and pressure, have the same number of molecules</em>.

The formula is:

\frac{V_1}{n_1} =\frac{V_2}{n_2}

Where V and n are volume and moles of the gas in initial and final conditions.

If the initial conditions are 0.0145 moles and 2.54L and final amount of moles is 0.0253moles, final volume is:

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V₂ = <em>4.43L is final volume of the ballon</em>

6 0
3 years ago
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