Molar and mass flow rate question?

Question

Question:

A 6M sulfuric acid solution (H2SO4 in water) is flowing into a tank at the rate of 100 L/min. The density of the solution is 1.34 g/cm3. Determine the:

b) The molar flow rate of H2SO4 into the tank

c) The mass flow rate of H2SO4 into the tank

d) The total mass flow rate into the tank

i have determined the mass flowrate to be m = 1.34 x 10^5 g/L and the molar flowrate to be 1367 mol/L, are these correct? I am just wondering where the 6M concentration comes into the questions because i have not used that yet to calculate (b & c).

Thanks

Answer 1

6M means that the concentration of acid is 6 mols/liter

"Rates" are in mols/minute, or grams/minute (not mol/L or g/L)

remember... when someone wants a 'rate' it is always something per unit of time

so, b) is easy.  6 mols/L * 100 L/min = 600 mols/minute

the 'Ls' cancel out so the units are mols/minute.

for c) you have to find the atomic weight of H2SO4, which is 1 + 1 + 32.07+ 16+16+16+16 = 98 g/mol BUT there are 6 of them per liter. So the total mass is 588 grams/L.   There are 100 L/min flowing, so we have 58,800 grams/minute of acid.  (Your teacher may or may not want you to account for the extra 0.07 g/mol in Sulpur in your calculations -- I didn't obviously).

for d) you use the density of the solution for the total mass flow rate.  There are 1000 cc/L, so the total mass/L is 1340 g/L.  Again, the rate is 100 L/min, so the total mass flow is 134000 g/min  You had your number correct, just not the units.

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Answer 2

1 lit solution contains 6 gram moles (98*6) = 588 g of H2 SO4.

a) So Molar flow rate of H2SO4 into the tank = 600 g moles / min

b) Mass flow rate of H2 SO4 = 58800 g / min = 58.8 kg/min

c) Total mass flow arte into the tank = 1.34*1000*100 = 134000 g/min = 134 kg/min