The mass of a glass beaker is known to be 24.2 g. approximately 5 ml of water are added, and the mass of the beaker and water is measured on an analytical balance to be 30.625 g. how many significant figures are there in the mass of the water?

2 significant figures in 6.4

Explanation:

Significant figures : The figures in a number which express the value -the magnitude of a quantity to a specific degree of accuracy is known as significant digits.

Rules for significant figures:

Digits from 1 to 9 are always significant and have infinite number of significant figures.

All non-zero numbers are always significant. For example: 654, 6.54 and 65.4 all have three significant figures.

All zero’s between integers are always significant. For example: 5005, 5.005 and 50.05 all have four significant figures.

All zero’s preceding the first integers are never significant. For example: 0.0078 has two significant figures.

All zero’s after the decimal point are always significant. For example: 4.500, 45.00 and 450.0 all have four significant figures.

Mass of beaker = 24.2 g

Mass of beaker + mass of water = 30.625 g

Mass of water = 30.625 - Mass of beaker = 30.625 - 24.2 = 6.4g

The rule apply for the addition and subtraction is :

The answer would contain same number of decimal places as there are in the least precise number present.

Thus there are 2 significant figures in mass of water which is 6.4 grams.