Question

suppose you have two samples that are equal in weight, 12.3 g sr and 12.3 g fe₂o₃. calculate the number of moles of each substance.
12.3 g sr = mol
12.3 g fe₂o₃ = mol

Explanation:

Step1: Determine molar mass of Sr

The molar mass of Sr (strontium) is approximately 87.62 g/mol.

Step2: Calculate moles of Sr

Use the formula $n=\frac{m}{M}$, where $n$ is the number of moles, $m$ is the mass, and $M$ is the molar mass. For Sr, $n_{Sr}=\frac{12.3\ g}{87.62\ g/mol}\approx0.113\ mol$.

Step3: Determine molar mass of Fe₂O₃

The molar mass of Fe is approximately 55.85 g/mol and of O is approximately 16.00 g/mol. For Fe₂O₃, $M = 2\times55.85\ g/mol+3\times16.00\ g/mol=159.7\ g/mol$.

Step4: Calculate moles of Fe₂O₃

Using the formula $n=\frac{m}{M}$, for Fe₂O₃, $n_{Fe_2O_3}=\frac{12.3\ g}{159.7\ g/mol}\approx0.077\ mol$.

Answer:

12.3 g Sr = 0.113 mol
12.3 g Fe₂O₃ = 0.077 mol