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# Tutor profile: Thomas D.

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Thomas D.
Adjunct Instructor and High School Teacher
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## Questions

### Subject:Physics (Waves and Optics)

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Question:

Calculate the energy of a 532 nm photon in Joules.

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Thomas D.

Planck's constant relates energy of a wave to its wavelength using E=hc/λ where E is the energy of the wave, h is planck's constant (6.626x10^-34 J*s), c is the speed of light (3x10^8 m/s), and λ is the wavelength of the wave in meters. First, change the wavelength from nm to m. 532 nm / (1x10^9 nm/1 m) = 5.32x10^-7 m. Plugging in the constants and the wavelength, E=(6.626x10^-34 J*s)(3x10^8 m/s)/5.32x10^-7 m. Which equals 3.73x10-19 J of energy.

### Subject:Pre-Calculus

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Question:

Simplify cos(x)/tan(x)

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Thomas D.

The answer is csc(x). tan(x) is sin(x)/cos(x). Plugging this in we get, cos(x)/sin(x)/cos(x). The cos(x) cancel giving 1/sin(x) which is csc(x).

### Subject:Chemistry

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Question:

What is the empirical formula for a compound with 16 g of oxygen 3 g of hydrogen and 12 grams of carbon?

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Thomas D.

You must first find the molar ratios of each element in the compound. Oxygen's molar mass is 16 g/mol, hydrogen is 1 g/mol, and carbon is 12 g/mol. Therefore, there is 16 g/(16g/mol)= 1 mole of oxygen. There is 3 g/ (1g/mol)= 3 moles of hydrogen. There is 12 g/(12 g/mol)= 1 mole of carbon. Therefore the ratio of O:H:C is 1:3:1. So the formula is CH3O.

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