# Pls can someone help me to solve this question, am practicing for my exams.

The specific heat capacity of water is 4.184 J/g°C. A 500g sample of water is exposed
to the light emitted by a CO2 laser. The wavelength of the laser light is 1.06 × 104 nm.
Assuming that all of the light energy is converted into heat, calculate the number
moles of photons required to raise the temperature of the water by 2°C.

sorry folks, can anyone give me a little insight about BONDING and ANTI-BONDING ORDER in MOLECULAR ORBITAL.

cheers alot. SmokeE

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HallsofIvy
Homework Helper
I have no idea about "bonding" and "anti-bonding" but the first part of your question is just a matter of arithmetic. You are asked about raising the temperature of the water 2°C so that will require (4.184 J/g°C)(2°C)= 8.368 J/g. You have 500 g of water so that will require (8.368 J/g)(500 g)= 4184 J.

Now, how much energy does a photon of light at 1.05 x 104 nm (was that 10-4? It couldn't be just 105*104 nm or 105 x 104 nm and still be "light".)
have? Divide 4184 J by that to see how many photons are required.

@hallsofivy - thanks for the reply its 105*10^4 nm =105*10^-5 m because nm = 10^-9

thanks alot it helped

sorry bro, will i not have to convert the 500g to Kg?

cheers

Borek
Mentor
Heat capacity is given per g, not per kg.

@ hallisofivy

Thanks for helping bro :L