posted by Sheryl on .
I did a lab where I had to decompose the compund patassium cholorate (KClO3)by heating,I had to weight the test tube then the test tube with the potassium chlorate to get the weight. I then had to heat it for several minutes and letting it cool down before weighing it again. Why must the test tube be cool before you weight it? I know because you can't touch it when it's hot, but I am sure there is another reason as well and I am not sure of it. Thank You
1. The "cold" test tube and contents won't weigh the same as the "hot" test tube and contents.
2. The hot tube will cause air currents to swirl around the balance or whatever weighing mechanism you are using and that will cause uncertainties in the weight of the tube and contents.
How to find the mass of Oxygen that displaces water from the in the decomposition reaction of potassium chlorate using manganese 4 oxide as a catalyst. Am I to use stoichiometry or the combined gas law equation P1V1/T1=P2V2/T2