AP Chemistry: A Sample Formal Laboratory Report
This paper is designed to help you prepare a chemistry lab report. Keep it in your chemistry notebook. All
chemistry lab reports must be written neatly and well organized to receive full credit. Lab reports may be written
or typed. It is highly recommended that you use graph or engineering bond paper for written reports.
Laboratory #7: Quantitative Determination of an Empirical Formula
I. Hypothesis: If nitric acid is poured onto tin, a tin oxide will be produced. If we know the initial mass of the tin
metal and the mass of the final product, we can determine the empirical formula of the tin oxide product.
There should be a whole number ratio between oxygen and tin. (The hypothesis explains what is to be
tested and will be written after reading the entire laboratory worksheet.)
II. Equipment:
(Non-chemical equipment used in the experiment.)
evaporating dish
forceps
watch glass
beaker
stirring rod
balance
burner with ring stand, ring and wire gauze
III. Reagents:
(A listing of chemicals used in the experiment with their amounts and any warnings.)
tin metal (granulated) ~2 g.
5 cm3 (mL) nitric acid (HNO3) caution! severe burns
IV. Procedure: Each step of the procedure must be written here. You may paraphrase and shorten the
explanations, but the reader must be able to perform the experiment from these instructions. (The
procedure must be read carefully before the lab begins. Drawings of the experimental setup may be
included here. The teacher may make changes to the procedure; make sure that you write any
changes down!)
V. Data:
(If the laboratory report is handwritten use a ruler to draw data tables and graphs! Always
include units with all data entries.)
Procedure
Trial 1
Trial 2
a mass of dish, and watch glass
74.14 g
b mass of dish, glass and tin
76.20 g
c mass of tin =b-a
d moles of tin
e mass of dish, glass, and product
f
mass of oxygen =e-b
g moles of oxygen
h mole ratio
i
accepted ratio
j
% error
2.06 g
.0173 mol
76.76 g
.56 g
.0350 mol
2.02 : 1
2:1
1.00 %
Chemistry/ Sample Laboratory Report
Laboratory #7, continued
VI. Calculations: (All calculations necessary for reaching the objective of the laboratory showing all
work with units and significant digits. Obvious calculations such as addition and subtraction need
not be included.
Moles of Sn =
mass of Sn
atomic mass of Sn
=
2.06 g
119 g/mol
=
.0173 mol Sn
Moles of O =
mass of O
atomic mass of O
=
0.56 g
16.0 g/mol
=
.0350 mol Sn
Molar ratio of oxygen to tin =
mol of O
mol of Sn
=
.0350 mol
.0173 mol
= 2.02 or 2 to 1
Experimental error = |experimental - theoretical| x 100 = |2.02 - 2| x 100 = 1.00 %
theoretical
2
VII. Data analysis/ conclusions: (This part succinctly explains what occurred during the
experiment, how the objective was reached and what the data tell us. Also, any special
circumstances or problems with the experiment are stated here. In quantitative labs, an error
statement with possible sources of error is necessary. This is the most important part of the
carefully!)
lab; write it
Nitric acid is a oxidizing agent. By allowing the nitric acid to react with the granulated tin metal we were
able to produce a tin-oxygen product called tin (X) oxide. By knowing the mass of the Sn reacted in the
experiment and the mass of the oxygen in the product, we were able to determine the empirical formula of the
product by converting these masses to moles and then dividing the greater mole quantity by the lesser. There were
2.06 g of Sn (.0173 mol) that reacted with .56 g O (.0350 mol.) The mole ratio of oxygen to tin in this experiment
is approximately 2 to 1. Since tin has potential oxidation numbers of 2+ and 4+ and oxygen 2-, the product tin
(IV) oxide (SnO2) is a possible product.
Our actual mole ratio of 2.02 to 1 is only 1% from the whole number ratio of 2 to 1. Possible sources of
error could arise from not allowing the product to dry enough, splattering of chemical during heating, and oxygen
is not the only gas in the atmosphere; a small amount of tin nitride my have been produced causing a difference in
the mass. If the experiment were repeated, the tin and nitric acid mixture must be heated slowly to prevent
splattering and loss a product.
Chemistry/ Sample Laboratory Report