Question

a chemist adds 1.05 l of a 9.0 × 10⁻⁴ m magnesium fluoride (mgf₂) solution to a reaction flask. calculate the moles of magnesium fluoride the chemist has added to the flask. be sure your answer has the correct number of significant digits.

Explanation:

Step1: Recall the formula for moles

The formula for moles ($n$) is $n = c\times V$, where $c$ is the concentration and $V$ is the volume.

Step2: Substitute the given values

Given $c = 9.0\times10^{-4}\text{ M}$ (which is $9.0\times10^{-4}\text{ mol/L}$) and $V = 1.05\text{ L}$.
Substitute into the formula: $n=(9.0\times 10^{-4}\text{ mol/L})\times(1.05\text{ L})$

Step3: Perform the multiplication

First, multiply the non - exponential parts: $9.0\times1.05 = 9.45$.
Then, keep the exponential part: $10^{-4}$.
So, $n = 9.45\times10^{-4}\text{ mol}$.

Step4: Consider significant figures

The concentration $9.0\times10^{-4}$ has 2 significant figures and the volume $1.05$ has 3 significant figures. In multiplication, the result should have the same number of significant figures as the least - precise measurement. So, we round $9.45\times10^{-4}$ to 2 significant figures. $9.45\times10^{-4}\approx9.5\times10^{-4}$

Answer:

$9.5\times 10^{-4}$