1 The specific heat of iron at 25 C is 0107 calg How much he

1) The specific heat of iron at 25* C is 0.107 cal/g. How much heat, in calories, does it take to warm 585g of iron from 3.00*C to 37.0*C?

2) A kettle contains 18 gal of tap water, which is alowed to evaporate. The solid material left behind has a mass of 1.7g. The hardness limit of dissolved solids is 51.4 mg/L. What is the mass in milligrams of dissolved solids per liter in the kettle?

Is the tap water considered to be hard?

3) Write the balanced equation for the reaction of slaked lime (calcium hydroxide) with alum (aluminum sulfate) to form aluminum hydroxide used in wasterwater treatment.

4) express each aquous concentration in the units indicated

a) 22 ug of trichloroethylene in 9.4L of water, as ppb of trichloroethylene.

b) 39g Cl2 in 1.00x10^4 L of water, as ppm Cl2

5) A .50L sample of drinking water is found to contain 2.0ug of toulene.

What is the concentraion of toulene in this sample?

Does this exceed the standard? (maximum contaminant level is 1.0 mg/L

6) How much calcium nitrate has to be added to 1000L of solution to provide 130ppm Ca^2+ if the water supply contains 40ppm Ca^2+?

b) How much NO3, in ppm, does this quantity of calcium nitrate add to the solution?

Solution

1) c = 0.107 cal/g T = 25C

C = 0.107/25 = 0.00428 cal/g-C

m = 585g

dT = 37-3 = 34C

q = m*C*dT = 585*34*0.00428 = 85.1292 calorie

2)

3) Al2(SO4)3 + 3Ca(OH)2 >> 2 Al(OH)3 + 3 CaSO4

4)

a) 1ppm = 1ug/ml

so 22ug in 9.4L = 22/9400ppm = 2.34*10^-3 ppm = 2.34 ppb

b)39g = 0.549 moles Cl2 = 12.3L Cl2

total volume = 10012.3L

39g in 10012.3L = 39000mg in 10012.3L = 3.895 ppm

5) mass = 2ug = 2*10^-6 g = 2.17*10^-8 moles

concentration = 2.17*10^-8/50 = 4.34*10^-10 M

concentration = 4*10^-5 ppm = 0.04ppb which is less than standard(800ppb)

6)extra Ca2+ added = 90ppm = 90 mg/L = 90000mg/1000L = 90g/1000L

= 2.25 moles Ca2+ /1000L = 2.25moles Ca(NO3)2 /1000L = 369g Ca(NO3)2

b)NO3- added = 4.5 moles /1000L = 4.5*10^-3 moles NO3-/L

= 0.279g/L = 279mg/l = 279ppm