Quantitative Analysis - in this lab, we will measure the quantity of a substance that is present in a chemical compound.
What we are going to do:
In this experiment, we are going to do the 1st of 2 quantitative analysis
● We are going to analyze a metal carbonate by weight some of that carbonate into a beaker
○ We will weigh a known amount in the beaker
● Then, we will out an excess of sulfuric acid in and then we will react the sulfuric acid with the carbonate
○ This will cause the carbonate to lose a certain amount of its weight as CO2 (carbon dioxide)
○ We will get a final weight of what the system weighs without that CO2 present
○ From the beginning weight and ending wight, we will be able to determine how much CO2 was lost, how many
moles of CO2 that equates to, then we will be able to go back and figure out how many moles that 1 gram (amount
of carbonate we start with) was equal to; which will then allow us to collect the molecular weight, and therefore
know what the carbonate was
Procedure:
● Start by putting the beaker and test tube in the balance, and tear it (zero it)
● Then, add about 1 gram of metal carbonate, a little at a time until reaching 1 gram
○ 1.1809 grams of metal carbonate
● Now we are going to add sulfuric acid
○ Put the sulfuric acid in the test tube but we are not interested in the weight of the sulfuric acid
○ Makes no difference how much sulfuric acid there is
○ Zero is once is has been added to the beaker in the test tube
○ We know there is 1.1809 g of metal carbonate
● Now, we are going to add the sulfuric acid into the carbonate
○ You will see it is fizzing and giving off carbon dioxide gas
○ See above equation
○ We want to get it to completely react so that we can find out what weight loss this has undergone
○ The mass loss/weight loss is due to the CO2 that is being lost by this compound reacting with the sulfuric acid
● So now we have to weigh everything that was on the scale together before
○ Means we have to add the test tube back in the beaker and re-weigh it to get the mass
● Mass that is lost as CO2 is 0.7033
○ Because we 0 the scale when putting everything together, now that i have added the sulfuric the figure on the
balance shows the amount of mass that was lost
○ Mass Loss of 0.7033
○ The mass that is lost as CO2
This study source was downloaded by 100000841138256 from CourseHero.com on 05-29-2023 02:13:08 GMT -05:00
Another Quantitative Analysis
● This time we are going to see how much water a hydrate will lose
● We have a sample of an unknown hydrate and we are going to figure out what it is
● What we are going to do:
○ Tear the container (we are using the crucible - a little casserole that we use in chemistry)
■ Can be heated very hot and cool it down; can withstand heat and won't crack
○ Add hydrate to the container to be weighed; we need to know how much hydrate we are adding
■ Add an amount that will make calculations easy
■ It is important to make measurements correctly as these are where results come from
■ We can add any amount, does not need to be certain; we want it in a particular way for calculations
○ We have added 2.4406 grams of metal hydrate
■ Now set up the device we use to heat it, and drive the water off
● We have the crucible set up with the unknown hydrate in it with a top on it to keep stuff from flying out or getting in
○ Put a burner under the crucible and let it heat the crucible for a while (10 minutes)
● What will happen:
○ The unknown hydrate in the crucible will lose its water
○ Why it is called a hydrate because it is holding several moles of water per mole of compound
○ The heat will drive the water out
● Without the top, we teared on the balance before placing on the heat
○ We will weight the crucible again afterwards without the top again, and the number that registers on the balance will
be the amount of weight/amount of mass lost
○ The hydrate will loss mass
● Once we are done heating it, we will put it in a container that will allow it to cool without picking the water back up
○ Called a desicater
10 minutes Later
● Now we will take the crucible off and put in the desicater to allow it to cool
○ Desicater has material in the bottom that will prevent the hydrate from picking any more water back up as it cools
since we have driven the water off
● Carefully remove the crucible and put it in the desicater
This study source was downloaded by 100000841138256 from CourseHero.com on 05-29-2023 02:13:08 GMT -05:00
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