Transcript Mathematical Operations in Chemistry

Mathematical
Operations in
Chemistry
Significant Figures
1. All non-zero digits are significant (2.45 has 3 SF)
2. Zeros between (sandwiched) non-zero digits are
significant (303 has 3 SF)
3. Zeros to the left of all non-zero digits are NEVER
significant (0.000025 has 2 SF and 00000125 has 3 SF)
4. Zeros to the right of all non-zero digits are only
significant if they are also to the right of the decimal
(250 has 2 SF and 250.00 has 5 SF)
5. A number ending in zero with a decimal place after it
indicates the zero is significant (350. has 3 SF)
5. Counting numbers have infinite significant figures (21
students has infinite SF)
6. Exactly defined quantities and conversion factors have
infinite significant figures (100 cm = 1 m – both terms
have infinite SF)
IMPORTANT NOTE


Significant Figures are used ONLY for
multiplication and division.
Places are used for addition and
subtraction.
Mathematical Operations
with Significant Figures
Multiplying and Dividing
The answer must be rounded to the same
number of significant figures as the number
in the problem with the least significant
figures.
7.83 kg
x2.1 kg
16.443 kg = 16 kg
Mathematical Operations
with Places
Adding and Subtracting_
The answer should have no more places
than the number in the problem with the
least places.
10.21 cm
+5.3 cm
15.51 cm = 15.5 cm