Lab 12

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LAB 12

Pre-Lab Questions:
See page(s) 1 for calculations

The purpose of this lab was to learn how to determine the percent of water in a hydrate.

Evaporating dishRing stand
Wire gauzeBurner
Crucible tongsTriple beam balance
Copper(II) sulfate penta-hydrateSpatula
Glass stirring rodDistilled water

See page(s) 1 and 2, for procedure steps 1-11

Observations and Data:
1. Mass of evaporating dish 21.48g
2. Mass of dish + hydrate 23.48g
3. Mass of dish + anhydrous salt 22.75g

See page(s) 3 and 4, for questions 1- 5

Questions for Discussion:
1. Sources of error in this lab could be caused by measuring the wrong amount of chemicals with the spatula, having left over water in the evaporating dish from not heating it well enough to evaporate all the water and reading the triple beam balance wrong or not knowing for to use a triple beam balance. You can prevent these types of mistakes by double checking your work and reading the directions carefully.

2.The percent composition of a component in a compound is the percent of the total mass of the compound that is due to that component. To calculate the percent composition of a component in a compound you have to find the molar mass of the compound by adding up the masses of each atom in the compound using the periodic table or a molecular mass calculator. Calculate the mass due to the component in the compound you are for which you are solving by adding up the mass of these atoms. Divide the mass due to the component by the total molar mass of the compound and multiply by 100.


In this lab we were asked to find the percent composition of a hydrate. Percentage composition refers to mass. When you are asked to determine the percentage composition of a compound, it should be understood that this refers to the percentage by mass. In other words, the percentage composition...
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