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# How to check if decomposition complete? Watch

1. In an experiment how can I check if decomposition complete? I know the mass will decrease but how will I know it's completed?

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2. If you know your starting mass and the product you expect to be left with, you should be able to calculate the expected mass once decomposition is complete.

You just need to use mole calculations and have an accurate balance.
3. To check decomposition is complete, you heat to a constant mass. So you heat it and weigh the mass of the residue, repeating this procedure until the mass of the residue is constant and does not change.
4. If gas is given off, you can measure the gas using a syringe. Record your readings and plot a graph, you will then see the point (with respect to time) where the volume of gas evolved decreases.

Meh, something along the lines of this anyway.

Or you could measure the mass of the starting product and check at regular intervals when the mass decreases to 0?

But the latter is probably not gonna work, because you always gotta take your test tube away from the bunsen.

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Updated: March 27, 2013
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