A student reacted 5.33 grams of cobalt with oxygen gas and obtained 7.50 grams of cobalt oxide. Determine the empirical formula of this cobalt-oxygen compound based upon this experiment.
5.33 g Co
7.50-5.33 = 2.17 g O
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mols Co = 5.33/58.93 = ?
mol O = 2.17/16 = ?
Find the ratio of the atoms to each other for the empirical formula.
Post your work if you get stuck.
To determine the empirical formula of the cobalt-oxygen compound, we need to calculate the ratio of cobalt to oxygen in the compound.
1. Convert the mass of cobalt to moles:
- The molar mass of cobalt (Co) is 58.933 grams/mole.
- Divide the mass of cobalt by its molar mass: 5.33 grams / 58.933 grams/mole = 0.0904 moles of cobalt.
2. Convert the mass of oxygen to moles:
- The molar mass of oxygen (O) is 16.00 grams/mole.
- Divide the mass of oxygen by its molar mass: 7.50 grams / 16.00 grams/mole = 0.4688 moles of oxygen.
3. Divide the moles of each element by the smallest number of moles:
- In this case, the moles of cobalt (0.0904) is the smallest.
- Divide the moles of cobalt and oxygen by 0.0904:
- Cobalt: 0.0904 moles / 0.0904 moles = 1
- Oxygen: 0.4688 moles / 0.0904 moles = 5.18
4. Round off the ratio to obtain whole numbers:
- Since we cannot have fractional subscripts in empirical formulas, we need to multiply the ratio by a common factor to get whole numbers. In this case, multiplying by 5 should suffice.
- The ratio becomes: Cobalt:Oxygen = 5:26.
5. Write the empirical formula:
- The empirical formula of the cobalt-oxygen compound based on this experiment would be Co5O26.