Question

q.15.how many moles of mg are there in 2.75g of mg? (7 p
show your work for full credit.report your answer to correct number of significant figures and units.
ans. given: 2.75g
find: moles of mg
conceptual plan:
2.75g × 1 mol / 24.30g=
solve:

a sample of copper wire has a mass of 32.5g. if the atomic mass of copper is 63.5g/mol, how many moles of copper are there.
report your answer to correct number of significant figures and with units.
given: 32.5g

Explanation:

Step1: Recall molar - mass formula

The formula to calculate the number of moles $n$ is $n=\frac{m}{M}$, where $m$ is the mass and $M$ is the molar mass. The molar mass of Mg is approximately $24.31\ g/mol$.

Step2: Substitute values

We are given $m = 2.75\ g$ and $M=24.31\ g/mol$. Substitute these values into the formula: $n=\frac{2.75\ g}{24.31\ g/mol}$.

Step3: Calculate the result

$n=\frac{2.75}{24.31}\ mol\approx0.113\ mol$ (rounded to three significant figures).

Answer:

$0.113\ mol$