HELP! Chemistry problem (Find number of protons)?

Question

The heat of fusion of ice is 6.00 kJmol−1. Find the number of photons of wavelength 5.58×10−6 m that must be absorbed to melt 1.70 g of ice.

Express your answer using three significant figures.

冷眼旁觀 · Answer

Molar mass of H₂O (ice) = (1.0×2 + 16.0) g mol⁻¹ = 18.0 g mol⁻¹
No. of moles of ice = (1.70 g) / (18.0 g mol⁻¹) = 0.09444 mol
Heat absorbed by ice = (6.00 kJ mol⁻¹) × (0.09444 mol) = 0.5666 kJ

Energy per photons = hc/λ = (6.626 × 10⁻³⁴ J s) × (3.00 × 10⁸ m s⁻¹) / (5.58 × 10⁻⁶ m) = 3.562 × 10⁻²⁰ J = 3.562 × 10⁻²³ kJ

No. of protons needed = (0.5666 kJ) / (3.562 × 10⁻²³ kJ photon⁻¹) = 1.59 × 10²² photons

Anonymous · Answer

energy needed = 1.7 g / 18.016 g/mole * 6000 J/mole = 566.2 J

Energy per photon = Planck's constant * speed of light / wavelength

# of photons = 566.2 J / energy per photon

A big number.

Trending News

HELP! Chemistry problem (Find number of protons)?

2 Answers