Microwave ovens use microwave radiation to heat food. The microwaves are absorbe
ID: 909627 • Letter: M
Question
Microwave ovens use microwave radiation to heat food. The microwaves are absorbed by the water molecules in the food, which is transferred to other components of the food. As the water becomes hotter, so does the food.
Part A
Suppose that the microwave radiation has a wavelength of 12.4 cm . How many photons are required to heat 215 mL of coffee from 25.0 C to 62.0 C? Assume that the coffee has the same density, 0.997 g/mL , and specific heat capacity, 4.184 J/(gK) , as water over this temperature range.
Express the number of photons numerically.
Part B:
The addition of hydrochloric acid to a silver nitrate solution precipitates silver chloride according to the reaction:
AgNO3(aq)+HCl(aq)AgCl(s)+HNO3(aq)
When you combine 50.0 mL of 0.110 M AgNO3 with 50.0 mL of 0.110 M HCl in a coffee-cup calorimeter, the temperature changes from 23.48 C to 24.45 C.
Calculate Hrxn for the reaction as written. Use 1.00 g/mL as the density of the solution and C=4.18J/gC as the specific heat capacity.
E
xpress your ans
wer with the appropriate units.
The free radical ClO is intimately involved in reactions that lead to the destruction of ozone in the stratosphere.
Part C
Given that a chlorine-oxygen bond in ClO2(g) has an enthalpy of 243 kJ/mol , an oxygen-oxygen bond has an enthalpy of 498 kJ/mol , and the standard enthalpy of formation of ClO2(g) is Hf=102.5kJ/mol, use Hess's law to calculate the value for the enthalpy of formation per mole of ClO(g).
Express your answer to two significant figures and include the appropriate units.
Microwave ovens use microwave radiation to heat food. The microwaves are absorbed by the water molecules in the food, which is transferred to other components of the food. As the water becomes hotter, so does the food.
Part A
Suppose that the microwave radiation has a wavelength of 12.4 cm . How many photons are required to heat 215 mL of coffee from 25.0 C to 62.0 C? Assume that the coffee has the same density, 0.997 g/mL , and specific heat capacity, 4.184 J/(gK) , as water over this temperature range.
Express the number of photons numerically.
Part B:
The addition of hydrochloric acid to a silver nitrate solution precipitates silver chloride according to the reaction:
AgNO3(aq)+HCl(aq)AgCl(s)+HNO3(aq)
When you combine 50.0 mL of 0.110 M AgNO3 with 50.0 mL of 0.110 M HCl in a coffee-cup calorimeter, the temperature changes from 23.48 C to 24.45 C.
Calculate Hrxn for the reaction as written. Use 1.00 g/mL as the density of the solution and C=4.18J/gC as the specific heat capacity.
E
xpress your ans
wer with the appropriate units.
The free radical ClO is intimately involved in reactions that lead to the destruction of ozone in the stratosphere.
Part C
Given that a chlorine-oxygen bond in ClO2(g) has an enthalpy of 243 kJ/mol , an oxygen-oxygen bond has an enthalpy of 498 kJ/mol , and the standard enthalpy of formation of ClO2(g) is Hf=102.5kJ/mol, use Hess's law to calculate the value for the enthalpy of formation per mole of ClO(g).
Express your answer to two significant figures and include the appropriate units.
Explanation / Answer
(2)
qrxn = msol X ssol X (t2 - t1)
qrxn = 100 X 4.18 X (24.45 - 23.48)
qrxn = 405.46 J