Question

please show the steps for A and B and C

A Heat is added to a pure substance in a closed container at a constant rate. The figure shows a graph of the temperature of the substance as a function of time. If Lf - latent heat of fusion and Ly - latent heat of vaporization, what is the value of the ratio Ly/L for this substance? Temp. A) 5.0 B) 4.5 Time C) 1.5 D) 3.5 E) 7.2 B Heat is added to a 2.0 kg piece of ice at a rate of 793.0 kW. How long will it take for the ice to melt if it was initially at 0.00°C? (The latent heat of fusion for water is 334 kJ/kg and its latent heat of vaporization is 2260 kJ/kg.) A) 0.84 s B) 4.7 s C) 530,000 s D) 670 s Two metal rods, one silver and the other copper, are both attached to a steam chamber as shown in the figure, with a temperature of 100°C, at one end, and an ice water bath, with a temperature of 0°C, at the other. The rods are 5.0 cm long and have a square cross-section, 2.0 cm on a side. When steady state has been reached, how much heat flows through the two rods in 1.0 min? The thermal conductivity of silver is 417 W/( m K), and that of copper is 395 W/( m K). No heat is exchanged between the rods and the surroundings, except at their ends. Silver Steam chamber Ice water Copper B) 47 kJ A) 39 kJ C) 20 kJ D) 49 kJ E) 11 kJ

Answer 1

Soln rate Let's say Joules / a constant Heat is supplied at During fision the time taken for fusion tre . " fos Valorisation For fusion exte = mx lf to Similarly for vabonigation extve mx lv - (11) from (i) and (11) 2 eto = 305 option ③ Ratio of L b Given mase of the = 20kg 793.0kW a addition Rate of heat 4 = 334 kJ/kg We know during meeting the tempo remains constant By energy balance 793 xpext = 2.0% 334x boy option A + 2x334 = 0.842 8

silver as 100 C Thay Coloper Sooms Let Area of base a 2x20 yam? as a heat transfer rate in silver at steady state Que " en in u cobber at 4 11 ec From Faurier's Law Qs = ks A (AT) = (417)(4x189(100 Sx102 Ocue Keu Alo?) = 395xuxloxid = 333-6 5 be = 316 318 ДУ SX Total heat flown in one second or = Ost Ocu = 649.65 Total heat flowns in one minute - 64906860 = 38976 J ↑ 39 KJ dation ④