The potassium chromium and oxygen compound has a relative molecular weight of 294. Establish the formula of the compound

| November 19, 2020 | education

The potassium chromium and oxygen compound has a relative molecular weight of 294. Establish the formula of the compound if the mass fraction of chromium in it is about 0.3537, and the number of potassium atoms is exactly the number of chromium atoms.

Decision:
1. The relative atomic mass of potassium is 39, chromium is 52, oxygen is 16.
2. Find the number of chromium atoms:
294 * 0.3537 / 52 = 104/52 = 2
3. The number of potassium atoms is 2, since their number is equal to the number of chromium atoms. Let’s find the mass of two potassium atoms:
39 * 2 = 78
4. The mass of oxygen atoms in the compound is:
294 – (78 + 52 * 2) = 294 – 78 – 104 = 112
5. Find the number of oxygen atoms:
112/16 = 7
The formula is K2Cr2O7. This is potassium dichromate.
Answer: the formula of the compound is K2Cr2O7.



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