Instructions:Read the lab first and then answer the pre-lab questions at the end.Bring the pre-lab questions and answers on a piece of paper to class with you on the day of the lab

 

 

Hydrate of Baking Soda Lab

Purpose:To determine the ratio of NaHCO3 (baking soda) to water by mass and by moles.Regular baking soda has a certain amount of water in it (this is called the hydrate).After heating, you will drive off the water and make baking soda anhydrate.

 

Safety:Remember that hot crucibles do not like cold water.ALWAYS WEAR GOGGLES!

 

Procedure:

  1. Find the mass of a crucible and cover on the balance.

Record mass of crucible and lid on data table.

††††† 2.Put enough baking soda into the crucible to fill the crucible up 1/3 of the way.

†††††††† ††Record the mass of crucible/lid and baking soda (hydrate) on the data table.

  1. Put the crucible/lid and baking soda on the clay triangle and begin to heat gently

†††††††††††† for 5 mintues.

  1. Take the crucible off the clay triangle (turn off the flame) and allow it to cool.When it is cool, find its mass and

†††††††††† Record as mass of crucible/lid and baking soda (anhydrate) 1 on the data table.

  1. Put the crucible back on the burner and begin to heat again for another 5 minutes.Again, allow it to cool when you are done and

††††† Record the mass of crucible/lid and baking soda (anhydrate) 2 on your data

††††† table.

6.If your value of anhydrate 1 and anhydrate 2 are within 0.1 grams of each other, you are ready to move on.If they are not, then reaheat the crucible until you do get results which are 0.1 gram different.

7.Clean up your lab area and do the questions.

 

Pre-Lab Questions:You do not need to copy the questions

 

  1. Should you ever weigh a crucible when it is hot?
  2. What is the name of the ďwetĒ baking soda?(Hydrate or Anhydrate)
  3. Is there any water in the Anhydrate?
  4. What is the chemical formula for baking soda?
  5. Why do you think you need to heat it again?

††††

 

Data Table:

 

mass of crucible and lid __________________g

mass of crucible/lid and baking soda (hydrate)_________________g

mass of crucible/lid and baking soda (anhydrate) 1_______________g

mass of crucible/lid and baking soda (anhydrate) 2†† _______________g

 

Caluclations:

1.Use your data table to figure out the following information:

mass of hydrated baking soda ____________________g

mass of anhydrated baking soda (your final result) ____________g

 

 

Post-LabQuestions:You donít need to copy the questions

1.How many grams of the baking soda hydrate is baking soda and how many grams is water?

2.What percentage of the total mass of the hydrated baking soda is Baking soda?

3.What percentage of the total mass of the hydrated baking soda is water?

4.Divide the smaller mass answer to question #1 into the larger mass answer.What is the mass ratio of baking soda:water?

5.Convert the number of grams of water in your hydrated sample into moles.

6.Convert the number of grams of baking soda (anhydrated) into moles.

7.What is the mole ratio of Baking soda:water?Remember, to find the mole ratio, convert all grams of substance into moles and divide by the SMALLEST number.

 

What is due for this lab and in what order?

1.Pre-Lab Questions (donít need to copy them)

2.Data table

3.Calculations

4.Post-Lab Questions(donít need to copy them)