Chemistry, 07.12.2019 06:31 maritsaledesma

A1.40-l gaseous system absorbs 75 j of heat and expands its volume to 2.00 l against an external pressure of 1.02 atm. what is the change in internal energy for this process? 1 $l_{atm}$ = 101.3 j

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Answer from: blumkemax8

15.24 J is the change in internal energy for this process.

Explanation:

According to the first law of thermodynamics:-

$\Delta U = q + w$

Where,

U is the internal energy

q is the heat

w is the work done

From the question,

q = + 75 J

(+ sign as the heat is being absorbed)

The expression for the calculation of work done is shown below as:

$w=-P\times \Delta V$

Where, P is the pressure

$\Delta V$ is the change in volume

From the question,

$\Delta V$ = 2.00 - 1.40 L = 0.60 L

P = 1.02 atm

$w=-1.02\times0.60\ atmL$

Also, 1 atmL = 101.3 J

So,

$w=-1.02\times0.60\times 101.3\ J=-59.76\ J$ (work is done by the system)

So,

$\Delta U = +75\ J-59.76\ J = 15.24\ J$

15.24 J is the change in internal energy for this process.

Answer from: Quest

Heat is involved in chemical change in two ways; chemical changes either result in heat being added to or removed from an object, and chemical changes require a certain amount of heat before they can take place.

Answer from: Quest

remember that hf is only the energy of one photon. not two. not three. one. 1) 5.12 * 10^3 photons find the energy of one photon, then determine how many photons are needed to reach the sensitivity. e = hf = (6.626 * 10^-34 js)(5.95 * 10^19 hz) = 3.94247 * 10^-14 j per photon (2.02 * 10^-10 j) / (3.94247 * 10^-14 j/photon) = 5123.69149 photons round to three sig figs. 2) 5.77 * 10^-17 j energy of pulse = energy per photon * number of photons = hfn = (6.626 * 10^-34 js)(1.66 * 10^13 hz)(5250) = 5.774559 * 10^-17 j round to three sig figs. 3) 4.07 * 10^8 kj/mol 10^12 pm = 1 m c = fλ f = c/λ e = hf = hc/λ = [(6.626 * 10^-34 js)(3.00 * 10^8 m/s) / (2.94 * 10^-12 m)](1 kj/1000 j)(6.02 * 10^23 photons/mol) = 40702571.4 kj/mol round to three sig figs. 4) 9.94 * 10^-1 m e = hc/λ λ = hc / e = (6.626 * 10^-34 js)(3.00 * 10^8 m/s) / (2.00 * 10^-25 j) = 0.9939 m round to three sig figs. 5) 9.06 * 10^3 photons energy of pulse = energy per photon * number of photons number of photons = energy of pulse / energy per photon = energy of pulse / (hf) = (3.87 * 10^-13 j) / [(6.626 * 10^-34 js)(6.45 * 10^16 hz)] = 9055.23695 photons round to three sig figs. 6) 2.78 * 10^-15 j this is problem 1, except in reverse. sensitivity = minumum number of photons * energy per photon = (5930)(6.626 * 10^-34 js)(7.077 * 10^14 hz) = 2.78070758 × 10^-15 j round to three sig figs.

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A1.40-l gaseous system absorbs 75 j of heat and expands its volume to 2.00 l against an external pre...

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