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Strike441 [17]
3 years ago
7

A lithium flame has a characteristic red color due to emissions of wavelength 671 nm. What is the mass equivalence of 1 mol of p

hotons of this wavelength (1 J = 1 kg·m²/s²)?
Chemistry
1 answer:
e-lub [12.9K]3 years ago
6 0

Answer:

1.98x10⁻¹² kg

Explanation:

The <em>energy of a photon</em> is given by:

  • E= hc/λ

h is Planck's constant, 6.626x10⁻³⁴ J·s

c is the speed of light, 3x10⁸ m/s

and λ is the wavelenght, 671 nm (or 6.71x10⁻⁷m)

  • E = 6.626x10⁻³⁴ J·s * 3x10⁸ m/s ÷ 6.71x10⁻⁷m = 2.96x10⁻¹⁹ J

Now we multiply that value by <em>Avogadro's number</em>, to <u>calculate the energy of 1 mol of such protons</u>:

  • 1 mol =  6.023x10²³ photons
  • 2.96x10⁻¹⁹ J *  6.023x10²³ = 1.78x10⁵ J

Finally we <u>calculate the mass equivalence</u> using the equation:

  • E=m*c²
  • m=E/c²
  • m =  1.78x10⁵ J / (3x10⁸ m/s)² = 1.98x10⁻¹² kg

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