PLEASE HELP!! 1) Microwave ovens heat food by creating microwave electromagnetic

Question

PLEASE HELP!!

1) Microwave ovens heat food by creating microwave electromagnetic radiation that is absorbed by water molecules in the food. Any material that does not have water in it will not absorb the radiation and will not get hot. Metals reflect the microwaves from their surfaces and disrupt the operation of the oven. Some Australians heat water in microwave ovens to make tea. What is the minimum number of microwave photons with a wavelength of 2.93 mm that will have to be absorbed by a 117.00 gram sample of water to heat it from 25°C to 100°C? (It requires about 315 joules of energy to heat 1 gram of water 75°C)

2) What is the frequency of a photon resulting from the transition of n = 7 n = 1 ? (give answer to 3 digits)

3) What is the formal charge on the C atom in the "best" Lewis structure for HCO3?

Explanation / Answer

heat energy required by water = 117gm* 315 joules/gm =36855 joules

from E= hc/wave length

E= hc/wave length = 6.627*10-34 joules/sec* 3*108 m/s/ 2.93*10-9 m =6.78*10-17 joules/ photon

number of photons = 36855 joules/ 6.78*10-17 = 5.43*1020 photons

2)

E= hv = RE*(1/nf2- 1/ni2), RE= 2.178*10-17 joules nf=7 and ni=1, h=6.627*10-34 J.s

v*6.627*10-34 = 2.178*10-17*(1-1/49)=3.22*1016 Hz

3. Formal charge = valence electrons in free atom-valence eletrons in bonded atom

there are 6 electrons in C and Charge =-1 (HCO3-)

so fomal charge 4-1=3

theere are 4 valence eletrons in oxygen and there is sharing of 4 eltrons with three of carbon electrons. hence remaining =3-4= -1

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