Chemistry questions

Question

A: A given element is found to contain 90% of isotope having a mass of 19.00 AMU and 10% of isotope having a mass of 21.00 AMU. What is the average atomic mass of the element?

B: In a neon light, when is the light emitted or given off?

C: How many of the three types of subatomic particles are present in an O-16 ion with a -2 charge? *

D: Infrared data transmission has a wavelength of 1.00 x 10^-5 m, what is the wave's frequency?

Answer 1

To find the average atomic mass of an element, we use the weighted average. This is found as follows:

(90%)(19.00 amu) + (10%)(21.00 amu) = (0.90 x 19.00) + (0.10 x 21.00) = 17.1 + 2.10 = 19.2 amu

The light is emitted when the gas is ionized by an electric current. Different gases give or or emit different colors. Neon gas emits an orange color.

O-16 (neutral) has atomic number 8 and atomic mass 16. Thus it would have 8 protons, 8 electrons and 8 neutrons. O-16^2- has gained 2 electrons so it has 8 protons, 10 electrons and 8 neutrons.

The relationship between wavelength and frequency is given by c = λν

c = speed of light (~3x10⁸ m/sec)

λ = wavelength = 1.00x10^-5 m

ν = frequency = ?

Solving for ν we have...

ν = c/λ = 3x10⁸ m/sec ÷ 1.00x10^-5 m = 3x10³ sec^-1 = 3000 Hz