Question

1. how many grams of carbon are in 15.0g of co₂?
2. how many grams of hydrogen are in 12.0g of h₂o?
3. what is the empirical formula of a compound that is made up of 24.5g of nitrogen and 70.0g of oxygen?
4. the elemental mass percent composition of ascorbic acid is 40.92% c, 4.58% h, and 54.5% o. determine the empirical formula for this compound.
5. upon combustion, a 0.8233 - g sample of a compound containing only carbon, hydrogen, and oxygen produces 2.445g co₂ and 0.6003g h₂o. determine the empirical formula of the compound.

Explanation:

7. How many grams of carbon are in 15.0g of CO₂?

Step1: Calculate molar mass of CO₂

The molar mass of C is 12.01 g/mol and O is 16.00 g/mol. So molar mass of CO₂, $M_{CO_2}=12.01 + 2\times16.00=44.01$ g/mol

Step2: Calculate mass of carbon

The mass - percent of C in CO₂ is $\frac{12.01}{44.01}\times100\%$. Mass of C in 15.0 g of CO₂, $m_C = 15.0\times\frac{12.01}{44.01}\approx4.09$ g

Step1: Calculate molar mass of H₂O

The molar mass of H is 1.01 g/mol and O is 16.00 g/mol. So molar mass of H₂O, $M_{H_2O}=2\times1.01+16.00 = 18.02$ g/mol

Step2: Calculate mass of hydrogen

The mass - percent of H in H₂O is $\frac{2\times1.01}{18.02}\times100\%$. Mass of H in 12.0 g of H₂O, $m_H=12.0\times\frac{2\times1.01}{18.02} = 1.34$ g

Step1: Calculate moles of N and O

Moles of N, $n_N=\frac{24.5}{14.01}\approx1.75$ mol. Moles of O, $n_O=\frac{70.0}{16.00}=4.375$ mol

Step2: Find mole - ratio

Divide each number of moles by the smaller number of moles. $\frac{n_N}{n_N}=1$, $\frac{n_O}{n_N}=\frac{4.375}{1.75}=2.5$. Multiply by 2 to get whole - numbers. The ratio of N:O is 2:5

Answer:

4.09 g

8. How many grams of hydrogen are in 12.0g of H₂O?