achieve #5

[KaylynnPierce2I]

I am just super confused on how to even start this question from achieve/homework; How many photons with a wavelength of 781 nm are needed to melt 477 g of ice? The enthalpy of fusion of water can be found in this table.

[Sammy Liu]

I am just super confused on how to even start this question from achieve/homework; How many photons with a wavelength of 781 nm are needed to melt 477 g of ice? The enthalpy of fusion of water can be found in this table.

1. Find the enthalpy of fusion of water (6.01 kJ/mol)
2. Convert the 477 grams of ice to moles of ice
3. Multiply the number of moles by the enthalpy of fusion of water to determine how much energy is required to melt the ice.
4. Save this number for later
5. Use the equation to find the amount of energy is in one photon of wavelength 781 nm
6. Take the number from step 3 and divide it by the amount of energy per photon calculated in step 5 to get the number of photons of wavelength 781 nm it takes to melt 477 g of ice.

Hope this helps!

[Jaylin Hsu 1C]

Hi, so the first step is to convert the 427 grams of ice into energy in Joules to find exactly how much energy is needed to melt the ice given in the question. You would use the conversion factor 333.6J/g to do this. Then, use the equation E=hc/lambda to find the energy of the a single photon with the given wavelength 745 nm. Lastly, divide the energy of the ice in Joules by the energy of a single photon also in joules to find the number of photons as asked in the question.

[Zoe Dhalla 3I]

Hello!

1. Start by determining the amount of energy needed to melt the given mass of ice. The enthalpy of fusion of water at 0 ∘C is 333.6 J/g. This means that it requires 333.6 J of heat energy to melt 1 g of ice. Multiply the enthalpy of fusion by the mass of ice to determine how much energy it takes to melt the ice.

2. The energy to melt the ice comes from the photons with a wavelength of 781 nm. The energy of one photon (E) is found using the equation E=hc/λ, where h is Planck's constant, 6.626×10−34 J·s, and c is the speed of light in a vacuum, 2.998×108 m/s. First, convert the wavelength in nanometers to meters. Then, plug the values into the equation.

3. Finally, to determine how many photons are needed, divide the energy needed to melt the ice by the energy of one photon.

Hope this helps!