[boarboy]

Hei, I know what follows is long but I really am uncertain about many of my answers and and anyone is able to confirm them and guide me on the right path for my uncertanties it would be greatly appreciated!!

1.Assume that wine is stored in a vessel containing 1ppm of lead. How much wine would an 80kg person have to drink to exceed 6ug/kg maximum recommended daily intake?

80kg person x (6.0x10^-6/1kg) x (106 g/1g lead ) = 480g wine       
   Is this correct?

2.Using the Wurtz reaction, what weight of sodium(kg) is required to fully dechlorinate a 108.0L sample of Alachor 1242 (42% Cl by weight; density = 1.211g/mL)

0.42 x 108.0L = 45.36L Cl = 45360ml Cl x (1.211g/ml)  = 54930.96 g Cl x (1kg/1000g) = 54.93096 kg Cl
Now I dont know how to use the Wurtz reaction to find the amount of Na needed. Is it exactly equivalent to the amount of Cl ?

3. in a waste to energy incineration plant, approximately 80% of municipal solid waste is combusted. The remainder is ash.
I am very confused with this entire question but I have made an attempt.
a. If we assume that the combustible fraction of MSW is primarily cellulose, with the empirical chemical formula CH2O and having a Hf = -212kj/mol, how much heat is released per tonne of MSW?

-212kj/mol x 1mol/30.026gCH20 x 1000000g/1 tonne = -7.06x10⁶kj/tonne

b. Asumming that fuel oil has the empirical formula CH2, a Hf = -30kj/mol and a bulk density  of 0.90 g/cm3, how many barrels(bbl) of oil would be required to generate the same amount of heat released in part (a) 1 bbl = 159 L.
 I have no idea how to start this one???

4. Tritium has a half life of 12.3 years.  How many years would it take for the radioactivity to decrease from 282,000 pCi/L to 20,000 pCi/L?
k = 0.693/t1/2  k = 0.693/12.3 = 0.05634 y-1
20,000/282,000 = 0.0709 so t = ln(0.07)/0.05634y-1 = 46.9734 years
   Is it correct?

5. Use the information below to calculate the energy release per mole in the nuclear reaction:
n + 142Ba + 91Kr + 3n

      Atomic mass
n      1.00866
235U      235.043922
142Ba      141.91645
91Kr      90.9234
   
235.043922 – ((2x1.00866) + 141.91645 + 90.9234 = 0.188g
E =mc² = 0.188x10^-3 kg x (2.99792x108 m/s)²   = 1.69x1013 kg m²/s² = 1.69x1013 J
        Right ??

Thank you very much!! any help is appreciated.
Joel

[MrOHBrown]

I shall assist you with this:

b. Asumming that fuel oil has the empirical formula CH2, a Hf = -30kj/mol and a bulk density  of 0.90 g/cm3, how many barrels(bbl) of oil would be required to generate the same amount of heat released in part (a) 1 bbl = 159 L.

OK, so we want to produce around 7 million kJ of energy, if each mole of fuel burnt produces 30 kj then:

Moles of fuel required = 7,000,000 / 30
                             = ~ 233333 Moles

Now lets find out how many moles are in one barrel:

159 litres of fuel = 159,000 cm³ of fuel

Now each cm³ of fuel has a mass of 0.9 g, so lets work how many moles of fuel are in 1 cm³ of fuel

molecular mass of fuel = ~14 g/n

Therefore Moles of fuel in 1 cm³ = 0.9 / 14
                                                           = 0.064 n
So how many moles of fuel are in a Barrel?

Moles CH2 in one barrel = 0.064 x 159,000
                                = 10176 moles

We need 233,333 moles to produce that much energy, so:

Barrels needed = 233,333 / 10,176
                     = ~ 23 barrels

I was pretty lax with my decimal points here, but use what I have done with more accurate numbers for a more precise result.

Also, if your answer for 3a turns out to be wrong, just plug the correct value into what I have done and adjust the numbers that follow accordingly.

[boarboy]

Thanks alot! very helpful!!!
I only hope part the rest including part a is right ??