It takes 245 kj/mol to eject electrons from a certain metal surface. what is the longest wavelength of light (nm) that can be used to eject electrons from the surface of this metal via the photoelectric effect?

longest wavelength is 489 nm

Explanation:

The energy per mol required to eject electrons from this  metal is given. We can calculate what is the energy required for one electron ( this value is known as the work function for the metal ), and from there make use of the equation: E = hc/λ to calculate the  wavelength, λ .

E = (245 x 10 ³ J / mol ) / 6.022 x 10²³ atom/mol = 4.1 x 10⁻¹⁹ J

E = h c/ λ   ⇒  λ = h c/ E

where h: Planck´s constant, 6.63 x 10⁻³⁴ Js

           c: speed of ligth, 3 x 10⁸ m/s

Therefore,

λ = 6.63 x 10⁻³⁴ Js x 3 x 10⁸ m/s/  4.1 x 10⁻¹⁹ J = 4.89 x 10⁻⁷ m

To convert to nm  multiply by the conversion factor, 1 x 10⁹ nm = 1 m

4.89 x 10⁻⁷ m  x 1 x 10⁹ nm /m = 489 nm

Therefore the maximum wavelength is 489 nm. Any light with a wavelength greater than this value will not have enough energy to eject electrons from this metal.

the correct answer is b. a strong acid completely dissociates to its ions when dissolved in water. completely dissociates to and ions. a is incorrect because does not fully ionize to and ions and some remain as the compound . c and d are incorrect because, and do not fall into the category of bronsted lowry acids. a bronsted lowry acid is a proton donor and since both molecules do not have a proton to donate they are not bronsted lowry acids. likewise,   if we use the lewis acid definition, they cannot be acids. a lewis acid is an electron pair acceptor. both and have a complete octet so can not accept any electrons which disqualifies them as acids.

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