2.19 for a k+−cl− ion pair, attractive and repulsive energies ea and er, respectively, depend on the distance between the ions r, according to e a = − 1.436 r e r = 5.86 × 10 − 6 r 9 ea=−1.436rer=5.86×10−6r9 for these expressions, energies are expressed in electron volts per k+−cl− pair, and r is the distance in nanometers. the net energy en is just the sum of the preceding two expressions. (a) superimpose on a single plot en, er, and ea versus r up to 1.0 nm. (b) on the basis of this plot, determine (i) the equilibrium spacing r0 between the k+ and cl− ions, and (ii) the magnitude of the bonding energy e0 between the two ions.

An electrical motor raises a 50kg load at a construct velencity .calculate the power of the motor, if it takes 40sec to raise the load through a height of 24m(take g =9.8n/g)

Air is to be cooled in the evaporator section of a refrigerator by passing it over a bank of 0.8-cm-outer-diameter and 0.4-m-long tubes inside which the refrigerant is evaporating at -20°c. air approaches the tube bank in the normal direction at 0°c and 1 atm with a mean velocity of 4 m/s. the tubes are arranged in-line with longitudinal and transverse pitches of sl- st 1.5 cm. there are 30 rows in the flow direction with 15 tubes in each row. determine (a) the refrigeration capacity of this system and (b) pressure drop across the tube bank. evaluate the air properties at an assumed mean temperature of -5°c and 1 atm. is this a good assumption?

For the closed feedwater heater below, feedwater enters state 3 at a pressure of 2000 psia and temperature of 420 °f at a rate of ix10 ibhr. the feedwat extracted steam enters state 1 at a pressure of 1000 psia and enthalpy of 1500 btu/lbm. the extracted er leaves at an enthalpy of 528.7 btu/lbm steam leaves as a saturated liquid. (16) a) determine the mass flow rate of the extraction steam used to heat the feedwater (10) b) determine the terminal temperature difference of the closed feedwater heater