Experiment 5: Law of Definite Composition Pre lab Assignment 1. Irwin the Introd

Question

Experiment 5: Law of Definite Composition Pre lab Assignment 1. Irwin the Introductory Chemist conducts this experiment. The test tube he uses weighs 5.624 g. potassium chlorate, the mass of the test tube+potassium chlorate is 6.754g.After heating the sample, the cooled test tube+sample weighs 6.460 g. Calculate the following and show all work After adding a. Mass of potassium chlorate: b. Mass of KCI: C. Mass of oxygen driven off: d. Mass ratio of oxygen/KCl: 2. If there are three oxygen atoms in the potassium chlorate chemical formula (KCIO,), what should be mass ratio of oxygen/KCI be? Show all work 3. Do you expect this ratio to change if you change the mass of your KCIO, sample? Why/why not? 4. Give two reasons why the test tube should be cool before weighing.

Explanation / Answer

Given mass of tube = 5.624 g

Mass of tube + potassium chlorate = 6.754 g

Mass of potassium chlorate = 6.754 g - 5.624 g = 1.13 g Answer

2 KClO3 (s) + heat ----> 2 KCl (s) + 3 O2 (g)

2 moles 2 moles 3 moles

Mass of test tube + sample = 6.460 g

KCl will be reamining when we heat and then cool the tube O2 will be vaporized

Mass of sample (i.e KCl) = 6.460 g - 5.624 g = 0.836 g Answer

Mass of oxygen driven off = 1.13 g - 0.836 g = 0.294 g Answer

Mass ratio of oxygen/KCl = 0.294 g / 0.836 g = 0.352 Answer

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