[Lialani]

In chemistry we did a lab to determine the atomic weight of a metal by converting the metal to an oxide by adding nitric acid.

The Procedure:
1. Heat two crucibles and covers in a sand bath overnight.
2. Cool, then transfer to an analytical balance and mass each crucible.
3. Place 1g of metal foil in each crucible and re-mass.
4. Place crucible in sandbath.
5. Add about 5 mL of concentrated nitric acid, sit the cover ajar, let it heat until dry.
6. Let cool, mass.

There are 2 questions that I'm currently confused on.

1. Identify two possible procedural errors that could make your determined value of the atomic weight too high, and identify two other errors that could make it too low. Explain.

I have: Two errors that make it too high is spattering the nitric acid when adding it and touching the crucible before putting it in the sandbath the second time after it is already massed.
Then i have touching the crucible after nitric acid has already been added and evaporate and before the remassing of the crucible will make the atomic weight lower.

I was wondering if those were right and what other errors whould make the value of the atomic weight too low.

2. In a variant of this experiment a weighed amount of metal can be treated with hydrochloric acid and converted to a chloride, which is then weighed. Just on a mass basis, which should give more precise results - formation of a chloride of formation of an oxide?

This one i'm really clueless on. Would it be formation of a chloride because chloride has a greater atomic weight so the readings would be more accurate than oxide?

  please help. thank you.

[Borek]

chloride has a greater atomic weight so the readings would be more accurate than oxide?

Exactly.

[Lialani]

Exactly.

Thanx
is the answer to the other questions right?

[Borek]

If the sandbath temperature is too low you may have incomplete decomposition of nitrate.

[Lialani]

I already turned in my lab but thank you for answering me