What is the empirical formula of a compound that is 14 g calcium, 11 g oxygen, and 0.7 g hydrogen?
A. CaO2H
B. Ca2OH2
C. CaOH
D. Ca(OH)2
Convert grams to mols.
14/atomic mass Ca = ?
11/atomic mass O = ?
0.7/atomic mass H = ?
Now find the ratio of these elements to each other with the smallest being 1. The easy way to do this is to divide the smallest number by itself, then divide all of the other numbers by the same small number. If you have numbers from that less than one, scale it up to make the smallest 1. Post your work if you get stuck.
To determine the empirical formula of a compound, you need to find the simplest whole-number ratio of the elements present in the compound. Here's how you can do it:
1. Convert the given masses of each element to moles.
- Calcium (Ca): 14 g / molar mass of Ca
- Oxygen (O): 11 g / molar mass of O
- Hydrogen (H): 0.7 g / molar mass of H
2. Calculate the mole ratio between the elements. Divide each number of moles by the smallest number of moles obtained to get a whole-number ratio.
3. Write the empirical formula using the whole-number ratio determined in the previous step.
Let's calculate it step by step:
1. Molar mass of each element:
- Ca: 40.08 g/mol (from the periodic table)
- O: 16.00 g/mol (from the periodic table)
- H: 1.01 g/mol (from the periodic table)
2. Moles of each element:
- Ca: 14 g / 40.08 g/mol = moles of Ca
- O: 11 g / 16.00 g/mol = moles of O
- H: 0.7 g / 1.01 g/mol = moles of H
3. Divide by the smallest number of moles:
- Divide all moles by the lowest number of moles you obtained to simplify the ratio. In this case, the lowest number of moles is moles of O.
4. Simplified mole ratio:
- Moles of Ca: Moles of O: Moles of H
5. Write the empirical formula:
- The empirical formula should give the simplest whole-number ratio of the elements.
Now, let's calculate the empirical formula:
Moles of Ca: Moles of O: Moles of H (Simplified ratio)
Finally, write the empirical formula using the multiplied values as subscripts of the respective elements:
A. CaO2H (incorrect)
B. Ca2OH2 (incorrect)
C. CaOH (correct)
D. Ca(OH)2 (incorrect)
Therefore, the correct answer is C. CaOH.