Chem 2.2 Measurement and significant figures

Question 0

Placeholder zeros

Answer 0

Are neither certain nor estimated. They make a number bigger or smaller. NOT SIGNIFICANT
ex. 2300 230 0.023

Question 1

In a measurement, you need to write

Answer 1

All certain digits and the last estimated digit (uncertain)

Question 2

Non-placeholder zeros are

Answer 2

certain or estimated. They ARE SIGNIFICANT

Ex. 203 23.0

Question 3

Rule #1

Answer 3

All non-zero numbers are significant

Ex. 23.5

Question 4

Rule #2

Answer 4

Zeros at the beginning of a number are never significant

Ex. 0.023 0.4

Question 5

Rule #3

Answer 5

Zeros at the end of a number are not significant unless there is a decimal point in the number
Ex. 50= 1 sig fig 54.60 = 4 sig figs

Question 6

Rule #4

Answer 6

Sandwiched zeros are significant

Ex. 203 5402

Question 7

Rule #5

Answer 7

For a number expressed in scientific notation all digits in the coefficient are significant

Question 8

Rule #6

Answer 8

Exact number (no doubt or uncertainty of values) always have infinite numbers of sig figs