1) A spherical ball of lead has a diameter of 4.00 cm. What is the mass of the sphere if lead has a density of 11.34 g/cm3. (The volume of a sphere is (4/3) πr3 where r is the radius.)

_______g

2) An experiment requires 15.1 g of cyclohexane, whose density at 25°C is 0.7781 g/mL. What volume of cyclohexane should be used?

_________ml

3)A cylindrical rod formed from silicon is 16.3 cm long and has a mass of 2.11 kg. The density of silicon is 2.33 g/cm3. What is the diameter of the cylinder? (The volume of a cylinder is given by πr2h, where r is the radius, and h is its length.)

________cm

4) After the label fell off a bottle containing a clear liquid believed to be benzene, a chemist measured the density of the liquid to verify its identity. A 25.0-mL portion of the liquid had a mass of 21.95 g. A chemistry handbook lists the density of benzene at 25°C as 0.8787 g/mL. Is the calculated density in agreement with the tabulated value?

A - Yes B - No

PLEASE HELP!!

## Answers (1)

1.)

Solve for volume:

V = (4/3) π r^3

V = (4/3) π (2 cm)^3

V = 33.5 cm^3

Find mass:

Density = mass / Volume

(11.34 g/cm^3) = mass / (33.5 cm^3)

mass = 379.89 g -- ANSWER!

2.)

Density = mass / Volume

0.7781 g/mL = (15.1 g) / (Volume)

Volume = 19.406 mL -- Answer!

3.)

Volume = mass / Density

V = (2.11 kg * 1,000 g / 1 kg) / (2.33 g/cm^3) = 905.58 cm^3

Find diameter (first find radius):

V = π r^2 h

radius = sqrt(V / π * h)

r = sqrt( 905.58 cm^3 / π * (16.3 cm) )

r = 4.205 cm

Diameter = Radius * 2 = 4.205 cm * 2 = 8.41 cm -- ANSWER

4.)

D = m / V = 21.95 g / 25 mL = 0.878 g/mL

Answer is B - No

(The calculated density was 0.878 g/mL NOT 0.8787 g/mL)

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I hope you understand and do not just copy. These are very important concepts.