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Cerrena [4.2K]
3 years ago
7

3.) A 208 g sample of sodium-24 decays to 13.0 g of sodium-24 within 60.0 hours.

Chemistry
1 answer:
Ulleksa [173]3 years ago
3 0

Answer:

Half life = 12 hrs

Explanation:

Given data:

Total amount of sample = 208 g

Amount left after 60 hr = 13.0 g

Half life = ?

Solution:

Step one:

amount             half life

208 g                    time 0

208/2                   1 half life

104/2                    2 half life

52/2                     3 half life

26/2                     4 half life

13                         5 half life

Step 2:

half life = elapsed time/ total half life when 13 g is left

Half life = 60 hrs/ 5

Half life = 12 hrs

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Number of moles:

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From the equation, 2 moles of Al give off 849 kJ of heat :

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