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Alex787 [66]
3 years ago
10

Which of these is true concerning an endothermic reaction? *

Chemistry
1 answer:
Anna [14]3 years ago
5 0

Answer:

A system absorbs more energy than it releases and has a positive AH  

Explanation:

Answer:

Explanation:

Endothermic (endo = into + thermic = heat) means that heat energy is going into a system.

The products will have more energy than the reactants and ΔH will be positive.

A is wrong, because ΔH is positive.

C and D are wrong, because the system absorbs more energy than it releases.

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What is the threshold frequency ν0 of cesium?
Montano1993 [528]
 I think this is what you're after:

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Convert to J and divide by the Avogadro Const to give E in J per photon 


E = 375700/6.022×10^23 = 6.239×10^-19 J 


Plank relationship E = h×ν E in J ν = frequency (Hz s-1) 


Planck constant h = 6.626×10^-34 J s 


6.239×10^-19 = (6.626×10^-34)ν 


ν = 9.42×10^14 s^-1 (Hz) 


IP are usually given in ev Cs 3.894 eV 


<span>E = 3.894×1.60×10^-19 = 6.230×10^-19 J per photon </span>

4 0
3 years ago
Does density depend on the amount of substance that you have? Explain your answer.
Natasha_Volkova [10]

Answer:

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3 0
4 years ago
"I think of a number, multiply it by itself and then add 6 to the result<br>+​
Sonja [21]

Answer:

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5 0
3 years ago
How many photons are produced in a laser pulse of 0.862 J at 691 nm?
Inga [223]
To calculate how many photons are in a certain amount of energy (joules) we need to know how much energy is in one photon.
Start by using two equations:
Energy of a photon = Frequency * Planck's constant (6.626 * 10^(-34) J-s)
Speed of light (constant 3 * 10^8 m/s) = Frequency * Wavelength
Which means:
frequency = Speed of Light / Wavelength
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You may have seen this equation as E = hc/<span>λ</span>
We have a wavelength of 691 nm or 691 * 10^-9 meters
So we can plug in all of our knowns:
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,so divide joules by joules per photon, and we have the number of photons:
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4 0
3 years ago
How many single covalent bonds can halogens form?
Simora [160]
One single covalent bond, hope this helps!
4 0
3 years ago
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