Q1) A chemical plant produces an aqueous solution of sodium hydroxide that is 20

Question

Q1) A chemical plant produces an aqueous solution of sodium hydroxide that is 20% NaOH by mass. The company desires to produce a stream of 5% NaOH solution by diluting a stream of the 20% solution with the stream of pure water. What flowrates of pure water and the 20% stream will produce 1000 lbm/min of the 5% solution? (5 points)

Q2) Compare the atom economy of the LeBlanc process to that of the Solvay process for making sodium carbonate.

LeBlanc process: 2NaCl +H2SO4 + 2C + CaCO3 Na2CO3 + 2HCl + 2CO2 + CaS

Solvay process: 2NaCl + CaCO3 Na2CO3 + CaCl2

Q3) Find the process economy of producing 1000 tons of sodium carbonate per day via the Solvay process. Solvay process: 2NaCl + CaCO3 Na2CO3 + CaCl2; Given cost: NaCl = $95/ton, CaCO3 = $87/ton, Na2CO3 = $105/ton, CaCl2 = $250/ton. (10 points)

Q4) 500 lbm of nitrogen is to be charged into a small metal cylinder at 25 ºC, at a pressure such that the gas density is 11.5 kg/m3 .Without using a calculator, estimate the required cylinder volume.

Explanation / Answer

1]

Suppose there is 100g solution

100 g = 0.20 g of NaOH, 0.80 g of H2O = Q1

0.050 g NaOH =   0.950 gH2O = Q2

NaOH IN   = NaOH OUT

0.20*100 = 0.050 * Q2

Q2 = 400 g

100g + Q1 = Q2

Q1 = 300g H2O

Q1(g H2O)/100g solution = 3 g H2O)/100g

Q2(g H2O)/100g solution = 4 g H2O)/100g

1000lbm Product /min/ 400g product = 2.5 lbm/min/g

Solution flow rate = 100g* 2.5 lbm/min/g = 250 lbm/min/g

Dilution water flow rate = 300*2.5 = 750 lbm/min/g

= (250 +750 ) lbm/min/g = 1000 lbm/min/g

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