December 20, 2014

Homework Help: chemistry

Posted by Dina on Thursday, November 12, 2009 at 10:43pm.

was hoping someone can help me check if these answers make sense for a silver copper alloy lab.
3. Why donít you have to weigh the sodium chloride on a sensitive balance?
This one I am not sure about, It is because an excess of NaCl is needed to make sure the solution precipitates?

4. Why is it necessary to wash the precipitate?
To recieve an accurate reading on the mass of the precipitate.

5. Will the nitric acid in the wash water interfere with the weight of the silver chloride? (Nitric acid is prepared by dissolving the gas N2O5 in water.)
No because it is just excess water.

6. If the crucible containing the silver chloride is not cool when its mass is determined, will the calculated percent be too high or too low? Why?
It would be too high because the metal scale will contract with the heat and it will throw off the measurement.

7. Why donít we just use hydrochloric acid to both dissolve and precipitate the silver?
Because Hydrogen is soluble and no precipitate willl form.

8. Why is a special filter crucible rather than plain filter paper used?

The special filter is much lighter and it will give a more accurate reading on the final mass of the precipitate.

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