# JNTU II B.Tech I Semester Regular Examinations, November 2008

JNTU II B.Tech I Semester Regular Examinations, November 2008

CHEMICAL PROCESS CALCULATIONS

(Chemical Engineering)

SET-1

1. An aqueous solution K2CO3 contains 25% salt and the specific gravity of the solution is 1.53. Determine the following:

(a) The mole percent of the salt in the solution

(b) The molarity of the solution

(c) The molality of the solution

(d) The normality of the solution.

2. A mixture of ammonia and an air at a pressure of 730 mmHg and a temperature of 30 0C contains 5.1% NH3 by volume. The gas is passed at a rate of 100 cuft per min through an absorption tower in which only ammonia is removed .The gases leave the tower at a pressure of 725 mmHg, a temperature of 20 0C, and contain 0.05% NH3 by volume. Using ideal gas law calculate:

(a) Rate of flow of gas leaving the tower in cuft per minute

(b) Weight of NH3 absorbed in the tower per minute.

3. Write short notes on the following:

(a) Ideal solutions

(b) Liquefaction and Liquid state.

(c) Assumtions involved in derivation of clausius – clay perown equation.

4. The weather bureau reports a temperature of 90 0F, a relative humidity of 85% and a barometric pressure of 14.696 psia: at 900F water vapour pressure=1.4215 in Hg Antoine equation for water vapour pressure is given by log10p=7.3092- 1791.30 / T?35.05 Where p is kpa & T in k

(a) What is the molar humidity

(b) What is the humidity (Wt. basis)

(c) What is the percentage absolute humidity

(d) What is the dew point.

5. Pure carbon dioxide may be prepared by treating limestone with aqueous sulfuric acid. The limestone used in such a process contained calcium carbonate and magnesium carbonate, the remainder being inert insoluble materials. The acid used

contained 12% H2SO4 by weight. The residue from the process had the following

composition:

CaSO4 8.56%

MgSO4 5.23

H2SO4 1.05

Inerts 0.53

CO2 0.12

Water 84.51

During the process the mass was warmed and carbon dioxide and water vapor were removed.

(a) Calculate the analysis of the limestone used.

(b) Calculate the percentage of excess acid used.

6. The following catalytic reaction is carried out in gas phase:

C2H5OH(g) + 1/2 O2(g) ! CH3CHO(g) + H2O(g).

The ratio of air to ethanol in the fresh feed is 10 : 1. The conversion per pass through the reactor is 25%. The unreated ethanol is completely separated from the reaction products and is recycled. What is the ratio of recycle stream to fresh feed stream? What is the composition of the outlet stream from the reactor?

7. (a) Write Kopp’s rule. How this rule is useful in energy balance calculations.

(b) The heat capacity of SO2 is given by

Cp = a + bT?1 + CT?2.

Obtain an expression for mean heat capacity for sulfur dioxide.

8. The following reaction is carried out at a temperature of 4500C. Calculate the heat of reaction at this temperature.

N2(g) +3H2(g) ! 2NH3(g)

Standard heats of formation of NH3(g) = ?11.04 kcal/mol.

Heat capacities in cal/mol.K:

N2(g): Cp = 6.457+ 1.389 × 10?3 T ? 0.069 ×10?6 T2

NH3(g): Cp = 5.92 + 8.963 × 10?3 T ? 1.764 × 10?6 T2

H2(g): Cp = 6.946 ? 0.196 × 10?3 T + 0.4757 × 10?6 T2

T is in kelvin.