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ahrayia [7]
2 years ago
13

If the half-life of a radioactive substances is 590 million years and you have 40 atoms of it, how many half-lives will have pas

sed when 5 atoms remain
Chemistry
1 answer:
Nady [450]2 years ago
3 0

Answer:

3

Explanation:

Applying,

2^{n'} = R/R'............... Equation 1

Where n' = number of halflives that have passed, R = Original atom of the substance, R' = atom of the substance left after decay.

From the question,

Given: R = 40 atoms, R' = 5 atoms

Substitute these values into equation 1

2^{n'} = 40/5

2^{n'} = 8

2^{n'} = 2³

Equation the base,

n' = 3

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Answer:

0.259 kJ/mol ≅ 0.26 kJ/mol.

Explanation:

  • To solve this problem, we can use the relation:

<em>Q = m.c.ΔT,</em>

where, Q is the amount of heat absorbed by ice (Q = ??? J).

m is the mass of the ice (m = 100.0 g).

c is the specific heat of water (c of ice = 4.186 J/g.°C).

ΔT is the difference between the initial and final temperature (ΔT = final T - initial T = 21.56°C - 25.0°C = -3.44°C).

<em>∵ Q = m.c.ΔT</em>

∴ Q = (100.0 g)(4.186 J/g.°C)(-3.44°C) = -1440 J = -1.44 kJ.

<em>∵ ΔH = Q/n</em>

n = mass/molar mass = (100.0 g)/(18.0 g/mol) = 5.556 mol.

∴ ΔH = (-1.44 kJ)/(5.556 mol) = 0.259 kJ/mol ≅ 0.26 kJ/mol.

3 0
3 years ago
Which of the following is an example of a chemical change?
alexdok [17]

Answer:

Dissolving sugar in water, burning paper, and melting gold are all chemical changes

Explanation:

The action cannot be reversed, or undone. Therefore it is a chemical change.

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3 0
2 years ago
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Answer:funk

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Explanation:

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Answer:

The given electronic configuration is long hand notation.

Explanation:

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The given electronic configuration of potassium (K):  

The above configuration has all the electrons that are contained in the nucleus of an element. Thus, this configuration is a long-hand notation.

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xxTIMURxx [149]

Answer:

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