NAME DATE PERIOD PERCENT COMPOSITION OF OXYGEN

COVERAGE PERIOD [SEE INSTRUCTIONS] S UMMARY OF
0 21415 PERIODO OCHENTA Y SEIS DE
0 32737 PERIODO CIENTO CATORCE DE SESIONES

0 43752 PERIODO OCHENTA Y CINCO DE
0 43752 PERIODO OCHENTA Y CINCO DE
19 PERIODO CIENTO TRES DE SESIONES ORDINARIAS

NAME _______________________________	DATE______________	PERIOD _______

Percent Composition of Oxygen in KClO₃			LAB 4

PRELAB INFORMATION

Percent composition is the percent by mass of each element in a compound. The percent composition includes as many percents as there are elements in the compound. To determine the theoretical percent composition, one compares the mass of each element present in a one mole sample of the compound. This can be written:

% element = mass element (g)

molar mass compound (g)

In this laboratory investigation, you will heat potassium chlorate with a catalyst. The result will be the decomposition of potassium chlorate into potassium chloride and oxygen gas as seen in the balanced chemical equation:

MnO_2
(s)

NAME DATE PERIOD PERCENT COMPOSITION OF OXYGEN 2KClO_3(s) 2KCl_(s) + 3O_2(g)

PURPOSE

The purpose of this lab is to experimentally determine the percent composition of oxygen in potassium chlorate and then compare your results to the theoretical value.

HYPOTHESIS – Calculate the theoretical % composition of O in KClO₃ (use masses from the periodic table)

Calculation:

PROCEDURE

(follow written procedure; keep a record of the procedure in your lab book, but put it in your own words)

Mass an empty, clean dry test tube. Record.
Mass 1.00 g of potassium chlorate. Record. (Be sure to use weigh paper.)
Add the potassium chlorate to the test tube.
Mass 0.50 g of the catalyst manganese dioxide. Record.
Add the manganese dioxide to the potassium chlorate in the test tube.
Mix the two solids thoroughly by gently tapping the sides of the test tube.
U sing a test tube holder, tip the test tube and its contents until it is almost horizontal (70^o). Tap it gently until the contents are distributed evenly over the lower wall of the test tube (see the figure).

Holding the test tube at an angle and pointed away from others, move the test tube back and forth through the flame slowly and continuously, distributing the heat evenly over the entire length of the contents of the tube. Record your observations.
When no further changes to the matter are observed, approximately three minutes, stop heating and turn off the burner.
Let the test tube cool for approximately five minutes. Do not touch the bottom of the tube because the contents will remain hot for a longer time.
Mass the test tube and its contents. Record.
Place the waste as directed and clean up your workstation.

OBSERVATIONS/DATA

QUANTITATIVE DATA

Substance/Object	Mass (______)
Test tube
KClO₃
MnO₂
Test tube + contents after heating

QUALITATIVE DATA

Substance	Observations
KClO₃+ MnO₂ mixture before heating
Contents of test tube during heating
Contents of test tube after heating

CALCULATIONS

Using your data, calculate the mass of KCl produced.

Calculate the mass of the oxygen produced by the reaction.

ANALYSIS/CONCLUSIONS

Calculate the percent of oxygen in your sample of potassium chlorate. Use data from the lab.

Calculate you percent error for the lab by comparing the actual percent of oxygen (hypothesis) to the experimental value (#3).

2 PERIODO CIENTO TREINTA Y CUATRO DE
2 PERIODO NOVENTA Y CUATRO DE SESIONES
2 PERIODO NOVENTA Y TRES DE SESIONES

Tags: composition of, % composition, period, composition, percent, oxygen