Question

A compound is found to contain 30.45 % nitrogen and 69.55 % oxygen by mass. To answer the question, enter the elements in the order presented above. QUESTION 1: The empirical formula for this compound is . QUESTION 2: The molar mass for this compound is 46.01 g/mol. The molecular formula for this compound is .

Answer 1

Answer: The molecular formula of the compound is $NO_2$

Explanation:

Converting all these percentages into mass.

We take the total mass of the compound to be 100 grams, so, the percentages given for each element becomes its mass.So, the mass of each element is equal to the percentage given.

Mass of N = 30.45 g

Mass of O = 69.55 g

Step 1 : convert given masses into moles.

Moles of N=$\frac{\text{ given mass of N}}{\text{ molar mass of N}}= \frac{30.45g}{14g/mole}=2.175moles$

Moles of O = $\frac{\text{ given mass of O}}{\text{ molar mass of O}}= \frac{69.55g}{16g/mole}=4.347moles$

Step 2 : For the mole ratio, divide each value of moles by the smallest number of moles calculated.

For N = $\frac{2.175}{2.175}=1$

For O =$\frac{4.347}{2.175}=2$

The ratio of N: O = 1: 2

Hence the empirical formula is $NO_2$.

Empirical mass of $NO_2$ is = 14(1)+16 (2)=46

The equation used to calculate the valency is:

$n=\frac{\text{molecular mass}}{\text{empirical mass}}=\frac{46.01}{46}=1$

Step 3: To calculate the molecular formula=$n\times {\text {Equivalent Formula}}=1\times NO_2=NO_2$

Hence, the molecular formula of the compound is $NO_2$