## Process Calculations - Dec 2015

### Chemical Engineering (Semester 3)

TOTAL MARKS: 80

TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.

(2) Attempt any **three** from the remaining questions.

(3) Assume data if required.

(4) Figures to the right indicate full marks.
**1(a)** Two litres of NH_{3} at 30°C and 20.265 kPa is neutralized by 135 ml of solution of H_{2}SO_{4}. Find the normality of the acid.(5 marks)
**1(b)** The ground nut seeds containing 45° oil and 45° solids are fed to expeller, the cake coming out of expeller is found to contain 80° solids and 5% oil. Find the percentage recovery of oil.(5 marks)
**1(c)** A sample of petrol contains 15% H_{2} and 85% C by weight. Calculate the amount of air required for the complete combustion of 1kg of petrol. Find the composition of the dry products on volume basis if 15% excess air is supplied.(5 marks)
**1(d)** Define(i) Dry bulb temperature(ii) Absolute humidity(5 marks)
**2(a)** 5000 kg of Kcl are present in a saturated solution at 80°C. The solution is cooled to 20°C in an open tank. The solubilities of Kcl at 80°C and 20°C are 55 and 35 parts per 100 parts of water. i) Assuming water equal to 3% by weight of solution is lost by evaporation, calculate the weight of crystal obtained. ii) Calculate the yield of crystals neglecting loss of water by evaporation; Kcl crystallizes without ant water of crystals.(10 marks)
**2(b)** Make the following conversions: i) Pressure of 2 atm to mm Hg ii) 127 lb/ft^{3} to g/cm^{3} iii) 499 g of CuSO_{4}.5H_{2}O into moles iv) 3M k_{2}SO_{4} to g/l v) 4.8 mg/ml CaCl_{2} to normality.(10 marks)
**3(a)** The dilute acid containing 25% H_{2}SO_{4} is concentrated by commercial grade sulphuric acid containing 98% H_{2}SO_{4} to obtain desired acid containing 65% H_{2}SO_{4}. Find out the quantities of the acids required to make 1000 kg desired acid.(10 marks)
**3(b)** A feed to a continuous fractionating column analyses by wt.50% benzene and 50% tolune. The analysis of the distillate shows 95 wt% benzene and 8 wt% benzene as found in the bottom product. Calculate the amount of distillate and bottom product per 5000 kg of feed per hour. Also calculate % recovery of benzene.(10 marks)
**4(a)** Wood containing 40% moisture is dried to 5% moisture. What mass of water in kilogram is eveporated per kg of dry wood?(10 marks)
**4(b)** A sample of coal is found to contain 67.2% carbon and 22.3% ash(wt.basis). The refuse obtained at the end of combustion is analyzed to contain 7.1% carbon and the rest ash. Compute the % of the original carbon remaining unburnt in the refuse.(10 marks)
**5(a)** For the reaction A → B, the process flow diagram is shown in following figure. The fresh feed of A contains 0.6% of inerts by volume. Sixty five percentage conversion of A per pass is obtained. The concentration of inerts going into the reactor at point 1 must be held at 2.5% by volume. All streams are ideal gases and the process is steady-state

(i) How many moles need to be recycled per mole of total feed to the reactor at point 1? (ii) How many moles to be purged?

(iii) What is the overall conversion of A?

**5(b)**Calculate the heat that must be removed in cooling 32 kg of oxygen from 488 K(215°C) to 313 K (4.°C) using C

_{p}

C

_{p}°=a+bT+cT

^{2}+dT

^{3}(kJ/kmol-K)

gas | a |
b×10^{3} |
c×10^{6} |
d×10^{9} |

O_{2} |
26.0257 | 11.7551 | -2.3426 | -0.5623 |

**6(a)**Calculate the theoretical flame temperature of a gas containing 20% CO and 80% N

_{2}when burned with 100% excess air, both air and gas initially being at 25°C.

=-67,636 cal. T is in K and C

_{p}in cal/(gmol-K) in following eqs.

For CO

_{2}C

_{p}= 6.339+0.01014T - 3.146 × 10

^{6}T

^{2}2

For O

_{2}C

_{p}= 6.117+0.003167 -1.005 × 10

^{-6}T

^{2}

For N

_{2}C

_{p}= 6.457+0.001389T-0.069 × 10

^{-6}(10 marks)

**6(b)**Calculate the standard heat of reaction of the following reaction

2FeS

_{2}(s) +11/2 O

_{2}(g) → Fe

_{2}O

_{3}(s) +4SO

_{2}(g)

Compound Δ H

_{f}° (kj/gmol) at 25°C

FeS

_{2}(s) -178.02

Fe

_{2}O

_{3}(s) -822.70

SO

_{2}(g) -296.81(10 marks)