To find the product of sodium hydrogen carbonate when heated.

At the end of the experiment I will collect the gas and using a lit splint and limewater, I will discover what gas is given off and see if my prediction for the gas was correct.

To make it a fair test I will compare my results with those done by another person. I will measure my input variable correctly and keep the same crucible and lid throughout.

Apparatus

To conduct my experiment I will use:

> Bunsen burner and the safety equipment

> Crucible and lid

> Scales

> Tongs

> Gas testing equipment

Obtaining my Evidence

I am going to time each interval I have between measuring and heating, I am going to keep the same crucible and lid with the sodium hydrogen carbonate untouched throughout the investigation. This should keep it a fair test.

What I did to Obtain my Results

. I took the crucible and lid and weighed the two together; then I recorded the weight in the table below. Then I took a spatula full of sodium hydrogen carbonate and put that into the crucible and lid and weighed the whole thing and recorded the results in the table below. From this I worked out how much my sodium hydrogen carbonate was.

Object(s)

Weight (grams)

Crucible & lid

25.72 g

Crucible & lid and sodium hydrogen carbonate

26.72 g

Sodium hydrogen carbonate

g

I was very lucky with the amount of sodium hydrogen carbonate I had 'scooped' because it ended up being exactly 1g. I think this help with my results and the working out needed to discover the final formula.

2. I then began to heat the contents in the crucible and lid, above the Bunsen burner, for 90 seconds each time. I did this until the results table did not seem to be changing. The results stopped changing after 540 seconds. Here are my results for the weighing.

Time (secs)

Weight of crucible, lid and contents (grams)

90

26.28 g

80

26.26 g

270

26.26 g

360

26.26 g

450

26.26 g

540

26.26 g

This table shows that the sodium hydrogen carbonate has reduced in mass by 0.54g.

Calculations for final amount left - (26.72 - 26.26 = 0.46g the final sodium hydrogen carbonate, then 1g - 0.46g = 0.54g, the mass reduced).

3. I then took these results and put them into a table to try and discover the formula equation for sodium hydrogen carbonate, when it has been heated.

NaHCO3

NaxHyOz

Gas Product (carbon dioxide)

NaHCO3 = 84

23+1+12+48

=84

v

v

÷84

= 1 gram

NaHO = 40

23+1+16

= 38.64*

v

v

÷84

0.46 grams

CO2 =44

6+16+12

=44

v

v

÷84

= 0.53 grams

*this was easier to discover a formula, when I rounded the final atomic mass up to the nearest ten. Also in this column I worked from the bottom up to find the product outcome.

From this I can see that I was very close with my equations, so I am going to stick with my decision. That the gas product given off is Carbon Dioxide. If you look at the final amount at the bottom of each column, the two in the 'end product' columns add up to 0.99grams, which, in my conclusion the experiment, is very close to 1gram. So I am going to settle with this final solution.

I BELIEVE THAT THE OUTCOME OF SODIUM HYDROGEN CARBONATE (NAHCO3), WHEN HEATED, IS SODIUM HYDROXIDE (NAHO) AND THE GAS PRODUCT IS CARBON DIOXIDE (CO2).

Comparing my Results

Following up my investigation and results I decided to compare them with another person's, who had also been doing a similar experiment, under controlled conditions and kept fair.

Their results tables looked like this:

Object(s)

Weight (grams)

Crucible & lid

27.81 g

Crucible & lid and sodium hydrogen carbonate

28.67 g

Sodium hydrogen carbonate

0.84 g

Time (secs)

Weight of crucible, lid and contents (grams)

90

28.31 g

80

28.29 g

270

28.29 g

360

28.28 g

450

28.28 g

540

28.28 g

This table shows that the sodium hydrogen carbonate has reduced in mass by 0.54g.

Calculations for final amount left - (28.67 - 28.28 = 0.39g, the final sodium hydrogen carbonate, then 0.84g - 0.39 = 0.45g, the mass reduced).

NaHCO3

NaxHyOz

Gas Product (carbon dioxide)

NaHCO3 = 84

23+1+12+48

=84

v

v

÷100

= 0.84gram

NaHO = 40

23+1+16

= 39*

v

v

÷100

0.39 grams

CO2 =44

6+16+12

=44

v

v

÷100

= 0.44 grams

*this was easier to discover a formula, when I rounded the final atomic mass up to the nearest ten. Also in this column I worked from the bottom up to find the product outcome.

These results are almost identical to the ones I conducted myself. I looked closely at the bottom numbers and again, the last numbers at the bottom of the end two columns add up to make 0.83 grams, which is 0.01 grams off the sodium hydrogen carbonate. This also proves that the gas outcome is Carbon Dioxide.

Conclusion and Evaluation

I thought that if I put our results into a grid that I would see a big difference but I didn't. All I noticed from these is the dramatic drop in the first part of the heating process.

Compared to my prediction I am correct. I predicted that the gas outcome would contain carbon or hydrogen and the result was carbon dioxide. I also said that the first initial product (my input variable) would reduce in mass during the heating stage. For this I was correct. Also in my equation predicaments, I had predicted the equation:

NAHCO3 --> NaHO + CO2

And this equation was correct.

I would take my investigation and extend it further by collecting the gas and testing my results; putting my statement to the challenge! I feel my results were as accurate as they could be and that I managed to sustain a fair experiment. I think that if I was to ensure my measurements were correct then I would use a set of scales with a more definite measurement.

I feel this was a very good method to discover the answer to my investigation.

Chemistry Coursework Mr. Hillman

Vikki Stabler 10J 02/05/2007 - 1 -