Question

How many grams of oxygen are in 56 g of c2h2o2?

Answer 1

Answer: Mass of oxygen atom in given amount of compound is 30.88 grams.

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$  ....(1)

Given mass of $C_2H_2O_2=56g$

Molar mass of $C_2H_2O_2=58g/mol$

Putting values in above equation, we get:

$\text{Moles of }C_2H_2O_2=\frac{56g}{58g/mol}=0.965mol$

In 1 mole of $C_2H_2O_2$, 2 moles of carbon atoms, 2 moles of oxygen atoms and 2 moles of hydrogen atoms.

So, in 0.965 moles of $C_2H_2O_2$, moles of oxygen atoms will be = $\frac{2}{1}\times 0.965=1.93mol$

Calculating the mass of oxygen atoms by using equation 1:

Moles of oxygen atoms = 1.93 moles

Molar mass of oxygen atom = 16 g/mol

Putting values in equation 1, we get:

$1.93mol=\frac{\text{Mass of oxygen atom}}{16g/mol}\\\\\text{Mass of oxygen atom}=30.88g$

Hence, mass of oxygen atom in given amount of compound is 30.88 grams.

Answer 2

First, find percent of oxygen: atom/molecule... there are 2 atoms of Oxygen so: O2/C2H2O2 which is: 32g O2 / 58g C2H2O2 =32/58. 

Next, multiply this by the total mass (56g C2H2O2) and the units will cancel out (g*g/g -> g) leaving you with the mass of Oxygen: 

56g C2H2O2 * 32g O2/58g C2H2O2 = 56*32/58= 31g