Question

Consider two solids, one (A) with a density of 2.79 g/mL, and the other (B) with a density of 7.91 g/mL.

If you mix 1.00 g of each of the two substances together, what is the density of the mixture? --------g/ml

Answer 1

Answer:

Density ( ρ ) is a physical property found by dividing the mass of an object by its volume. Regardless of the sample size, density is always constant. For example, the density of a pure sample of tungsten is always 19.25 grams per cubic centimeter. This means that whether you have one gram or one kilogram of the sample, the density will never vary. The equation, as we already know, is as follows:

Density=MassVolume(4.9.1)

or just

ρ=mV(4.9.2)

Based on this equation, it's clear that density can, and does, vary from element to element and substance to substance due to differences in the relationship of mass and volume. Pure water, for example, has a density of 0.998 g/cm3 at 25° C. The average densities of some common substances are in Table 4.9.1 . Notice that corn oil has a lower mass to volume ratio than water. This means that when added to water, corn oil will “float.”

Table 4.9.1 : Densities of Common Substances

blood

1.035

body fat

0.918

whole milk

1.030

corn oil

0.922

mayonnaise

0.910

honey

1.420

Density can be measured for all substances, solids, liquids and gases. For solids and liquids, density is often reported using the units of g/cm3. Densities of gases, which are significantly lower than the densities of solids and liquids, are often given using units of g/L.

Example 4.9.1 : Ethyl Alcohol

Calculate the density of a 30.2 mL sample of ethyl alcohol with a mass of 23.71002 g

SOLUTION

ρ=23.71002g30.2mL(1000mL1L)Conversion Factor=0.785g/mL(4.9.3)