QUIZ 10

1. 5.0-L of alcohol solution (specific gravity = 0.60) is added to 4.0L of water to make a 9.0-L mixture, what is the specific gravity of the mixture?

Solution.

The definition of the specific gravity of the mixture is

            SG_mixture = r_mixture/r_water. 

The density of the mixture is

            r_mixture = m_mixture/V = (SG_alcoholr_waterV_alcohol + SG_waterr_waterV_water), so we get

            SG_mixture = (SG_alcoholV_alcohol + SG_waterV_wwater)/V

                             = [(0.60)(5.0L) + (1.0)(0.4L)]/(9.0L) = 0.78.

2. If each of the four tires of a 1500-kg automobile has area of 200cm² what is the gauge pressure (in atm) in each tire?

Solution.

We find the gauge pressure  from

            P = F/A = mg/A = (1500kg)(9.80m/s²)/(4)(200 x 10^-4m²)

                = (1.84 x 10⁵N/m²)(1atm/1.013 x10⁵N/m²)

                = 1.81atm.