I. (10 pts.) A fuel mixture is given as 20 mol% heptane (C7H16), 36 mol% hexane
ID: 701758 • Letter: I
Question
I. (10 pts.) A fuel mixture is given as 20 mol% heptane (C7H16), 36 mol% hexane (C6H14), and the remainder benzene (C&H6;). Determine the mass fraction of each component in the mixture. Fill in the table below with your answers Mole fraction Mass fraction Heptane (CHs Hexane (CsH4) Benzene (CoHs 0.20 0.36 (7 pt) The heat capacity of a material is 1.7 Btu/(bm F). What is the value of the heat capacity units of kJ/(kg K)? (9 pt) The pressure at the base of the 0.7 m column of liquid shown at right is easured as 16.5 psia. The top of the column is open to the atmosphere. What is the atm ecific gravity of the liquid? 0.Explanation / Answer
Ans 1
Basis 100 mol of fuel mixture
Moles of heptane = mol fraction of heptane x 100
= 0.20 x 100 = 20 mol
Mass of heptane = moles x molecular weight
= 20 mol x (7*12+1*16) g/mol
= 2000 g
Moles of hexane = mol fraction of hexane x 100
= 0.36 x 100 = 36 mol
Mass of hexane = moles x molecular weight
= 36 mol x (6*12+1*14) g/mol
= 3096 g
Moles of benzene = mol fraction of benzene x 100
= (1-0.20-0.36) x 100 = 44 mol
Mass of benzene = moles x molecular weight
= 44 mol x (6*12+1*6) g/mol
= 3432 g
Total mass = 2000 + 3096 + 3432
= 8528 g
Mass fraction of heptane = mass of heptane /total mass
= 2000/8528
= 0.2345
Mass fraction of hexane = mass of hexane /total mass
= 3096/8528
= 0.3630
Mass fraction of benzene = mass of benzene /total mass
= 3432/8528
= 0.4025