How can we make use of acids or bases to remove metals from soils?
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The answer is <span>(3) 3 × 12.4 hours
</span>
To calculate this, we will use two equations:
where:
<span>n - number of half-lives
</span>x - remained amount of the sample, in decimals
<span>
- half-life length
</span>t - total time elapsed.
First, we have to calculate x and n. x is <span>remained amount of the sample, so if at the beginning were 16 grams of potassium-42, and now it remained 2 grams, then x is:
2 grams : x % = 16 grams : 100 %
x = 2 grams </span>× 100 percent ÷ 16 grams
x = 12.5% = 0.125
Thus:
<span>
</span>
It is known that the half-life of potassium-42 is 12.36 ≈ 12.4 hours.
Thus:
<span>
</span><span>
</span>
Therefore, it must elapse 3 × 12.4 hours <span>before 16 grams of potassium-42 decays, leaving 2 grams of the original isotope</span>
</span>
To calculate this, we will use two equations:
where:
<span>n - number of half-lives
</span>x - remained amount of the sample, in decimals
<span>
</span>t - total time elapsed.
First, we have to calculate x and n. x is <span>remained amount of the sample, so if at the beginning were 16 grams of potassium-42, and now it remained 2 grams, then x is:
2 grams : x % = 16 grams : 100 %
x = 2 grams </span>× 100 percent ÷ 16 grams
x = 12.5% = 0.125
Thus:
<span>
</span>
It is known that the half-life of potassium-42 is 12.36 ≈ 12.4 hours.
Thus:
<span>
</span><span>
</span>
Therefore, it must elapse 3 × 12.4 hours <span>before 16 grams of potassium-42 decays, leaving 2 grams of the original isotope</span>
4V is the necessary voltage to power the electrolysis of molten sodium chloride.
To create sodium metal and chlorine gas, molten (liquid) sodium chloride can be electrolyzed. A Down's cell is the name of the electrolytic cell utilised in the procedure. The liquid sodium ions in a Down's cell are converted to liquid sodium metal at the cathode. Liquid chlorine ions are oxidised to chlorine gas at the anode. Below is an illustration of the reactions and cell potentials:
oxidation: →
+
E°= -1.36V
reduction: →
E°= -2.71V
overall : →
E°
= -4.07V
For this electrolysis to take place, the battery needs to supply more than 4 volts. The only means to obtain pure sodium metal is by this reaction, which also serves as a significant source of chlorine gas generation. Swimming pools and other surfaces are frequently cleaned and disinfected with chlorine gas.
Learn more about sodium chloride here;
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