Some Basic concepts of Chemistry Part - 3
Precision:
If indicates how closely repeated measurements match each other.
Accuracy:
It indicates how closely a measurement matches the correct or expected value.
Scientific Notation: Any
number can be represented in the form where n is an exponent having positive or
negative values and N can vary between 1 to 10. OR Expressing a number in the form
N × 10n, and N can vary between 1 to 10.
Significant figures: These
are meaningful digits which are known with certainty. The uncertainty is
indicated by writing the certain digits and the last uncertain digit. Thus, if
we write a result as 11.2 mL, we say the 11 is certain and 2 is uncertain and
the uncertainty would be 1 in the last digit.
There
are certain rules for determining the number of significant figures. These are:
1.
All non-zero digits are significant. For example,
in 285 cm, there are three significant figures and in 0.25 mL, there are two
significant figures.
2.
Zeros preceding to first non-zero digit
are not significant. Such zero indicates the position of decimal point. Thus,
0.03 has one significant figure and 0.0052 has two significant figures.
3. Zeros
between two non-zero digits are significant. Thus, 2.005 has four significant
figures.
4. Zeros
at the end or right of a number are significant if they are on the right side
of the decimal point; otherwise, they are not significant. For example, 0.200 g
has three significant figures.
5. Exact
numbers have an infinite number of significant figures. For example, in 2 balls
or 20 eggs, there are infinite significant figures since these are exact
numbers and can be represented by writing infinite number of zeros after
placing a decimal i.e., 2 = 2.000000 or 20 = 20.000000
When numbers are written in scientific
notation, the number of digits between 1 and 10 gives the number of significant
figures. For e.g. 4.01×102 has three significant figures, and 8.256
× 10–3 has four significant figures.
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