Question

+ Heating and Cooling Curves Constants Periodic Table Consider heating solid water (ice) until it becomes liquid and then gas (steam). (Figure 1) Alternatively consider the reverse process, cooling steam until it becomes water and, finally, ice. (Figure 2) In each case, two types of transitions occur, those involving a temperature change with no change in phase (shown by the diagonal line segments on the graphs) and those at constant temperature with a change in phase (shown by horizontal line segments on the graphs). Figure 1 of 2 Heating curve 100 Solid and liquid/ in equilibrium Solid Heat added (J)

Answer 1

く) 6of10 The heat energy associated with a change in temperature that does not involve a change in phase is given by where q is heat in joules, m is mass in grams, s is specific heat in joules per gram-degree Celsius, J/ (g-° C), and ΔΤ is the temperature change in degrees Celsius. The heat energy associated with a change in phase at constant temperature is given by where q is heat in joules, m is mass in grams, and Al is the enthalpy in joules per gram. Physical constants The constants for H2O are shown here Specific heat of ice: Sice 2.09 J/(g C) Enthalpy of fusion (H2O(s) H20(): AH . Specific heat of liquid water: Swater 4.18 J/(g C) 334 J/g . Enthalpy of vaporization (H2O(l)→H2O(g)):AHvap-2250J/g Part A How much heat energy, in kilojoules, is required to convert 37.0 g of ice at -18.0 C to water at 25.0 C? Express your answer to three significant figures and include the appropriate units Q = 37 x 18 x 2.09 + 37 x 334 + 37 x 25 x 4.18 Q17616 Joules or 17.616 Kilo Joules Part B How long would it take for 1.50 mol of water at 100.0 C to be converted completely into steam if heat were added at a constant rate of 25.0 J/s? Express your answer to three significant figures and include the appropriate units First let us calculate the heat is needed Mass of water 1.5 x 18 27 gm Q = 27 x 2250 = 60750 Joules Time is needed60750 252430 Seconds or 40.5 Minutes