Combined Mass?

Question

Calculate the mass in g of two solutions if one has a volume of 63.08mL and a density of 1.10 g/mL and the second has a volume of 61.67 mL with a density of 1.0225 g/mL. Express your answer correct to the appropriate number of significant figures.

Answer 1

Remember that density is the ration of the mass of an object to its volume,
Density = mass / volume.

If you know both an object's volume and density, you can calculate it’s mass.
mass = density * volume

You are given information about two solutions, you know both of their densities and volumes; from this you can easily calculate their mass.

One you know the mass of each solution; simply add the two together to obtain the combined mass of the mixture.

The Rules for determining the number of significant figures are:

1) Non zero digits - non-zero numbers are significant

2) Zeros - There are three types:
a) Leading zeros are zeros that precede all non-zero digits. These zeros are not significant figures.
b) Captive zeros are zeros between sig. figs., usually non-zero digits. These zeros are significant figures.
c) Trailing zeros are zeros at the right end of the number. They are sig. figs. only if the number contains a decimal point.

3) Exact numbers are numbers that are derived by counting or by definition (for example: π or the rest mass of an electron). These numbers have infinite number of sig. figs.


When performing calculations with sig. figs.:

Addition/Subtraction -The final answer should have the same number of digits to the right of the decimal as the measurement with the smallest number of digits to the right of the decimal place.

Multiplication/Division - The final answer should have the same number of significant figures as the measurement having the smallest number of significant figures.


Rounding:

Round Down
-Whenever the digit following the last significant figure is less than 5 (i.e. 0, 1, 2, 3, 4).
-If the last significant figure is an even number and the next digit is a 5, with no other non-zero digits.

Round Up
-Whenever the digit following the last significant digit is greater than 5 (i.e. 6, 7, 8, 9).
-If the digit following the last significant digit is a 5 followed by a non-zero digit.
-If the last significant digit is an odd number and the next digit is a 5, with no other non-zero digits.