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3 years ago

This exercise uses the radioactive decay model.

1 answer:

3 0

For radioactive decay, we can relate current amount, initial amount, decay constant and time using:
N = No x exp(-λt)

Half-life = ln(2)/λ
λ = ln(2) / 5730
N/No = 80% = 0.8
0.8 = exp( -ln(2)/5730 x t)
t = 1844 years

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Are nails in a jar with water a chemical change

Digiron [165]

I would say it is a chemical change because after a while, the nails start to rust. Now they only rust after about a week though. But rust is a chemical change.

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3 years ago

A chlorine atom has a diameter of 175 picometers (pm). Please write the diameter, in metered, in scientific notation.

Flauer [41]

Picometre is equal to 1·10⁻¹²m
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3 years ago

Explain how the mass of a single atom in an element (in amu), the mass of one mole of that element, and Avogadro’s number are re

Eva8 [605]

Answer: For 1 mole of a single atom it is equal to its molar mass. And a single atom, 1 mole is equal to the Avogadro's Number.

Explanation: The relationship can be expressed through the following:

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3 years ago

Bromine has two isotopes 79Br and 81Br, whose masses (78.9183 and 80.9163 amu) and abundances (50.69% and 49.31%, respectively)

Reika [66]

Answer:

Average atomic mass = 79.9034 amu

Explanation:

The formula for the calculation of the average atomic mass is:

$Average\ atomic\ mass=(\frac {\%\ of\ the\ first\ isotope}{100}\times {Mass\ of\ the\ first\ isotope})+(\frac {\%\ of\ the\ second\ isotope}{100}\times {Mass\ of\ the\ second\ isotope})$

Given that:

For first isotope:

% = 50.69 %

Mass = 78.9183 amu

For second isotope:

% = 49.31 %

Mass = 80.9163 amu

Thus,

$Average\ atomic\ mass=\frac{50.69}{100}\times {78.9183}+\frac{49.31}{100}\times {80.9163}\ amu$

$Average\ atomic\ mass=40.0036+39.8998\ amu$

Average atomic mass = 79.9034 amu

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3 years ago

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dem82 [27]

1. Crystallization. Magma cools either underground or on the surface and hardens into an igneous rock.
2. weathering and erosion
3. This happens due to geologic uplift and the erosion of the rock and soil above them. At the surface, metamorphic rocks will be exposed to weathering processes and may break down into sediment.
4. Rock Melting.
Metamorphic rocks underground melt to become magma. If you need more help https://www.ck12.org/earth-science/rock-cycle-processes/lesson/Rocks-and-Processes-of-the-Rock-Cycle-HS-ES/

8 0

3 years ago