Molarity is calculated by using following formula,

Molarity = Moles / Volume

Data Given:
Moles = 23 moles

Volume = 100 ml ÷ 1000 = 0.1 L

Putting values in eq. 1,

Molarity = 23 mol / 0.1 L

Molarity = 230 mol/dm³

Result:
When 23 mol of solute is dissolved in a solvent to make a solution of 100 ml, then it will have a Molarity of 230 mol/dm³.

3 0

4 years ago

A sample originally contained 1.28 g of a radioisotope. It now contains 1.12 g of its daughter isotope.

dexar [7]

The answer is 3.

The relation between number of half-lives (n) and decimal amount remaining (x) can be expressed as:

 $(1/2) ^{n} =x$

We need to calculate n, but we need x to do that. To calculate what percentage of a radioactive species would be found as daughter material, we must calculate what amount remained:
1.28 - 1.12 = 0.16

If 1.28 is 100%, how much percent is 0.16:
1.28 : 100% = 0.16 : x
x = 12.5%
Presented as decimal amount:
x = 0.125

Now, let's implement this in the equation:

 $(1/2) ^{n} =0.125$

Because of the exponent, we will log both sides of the equation:
$n * log(1/2) = log(0.125)$
$n = \frac{log(0.125)}{log(1/2)}$
 $n = \frac{log(0.125)}{log(0.5)}$
 $n= \frac{-0.903}{-0.301}$
$n = 3$

Therefore, 3 half-lives have passed since the sample originally formed.

4 0

3 years ago

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