Answer:
Option C = electron
Explanation:
Electrons are responsible for the production of colored light.
Electron:
The electron is subatomic particle that revolve around outside the nucleus and has negligible mass. It has a negative charge.
Symbol= e-
Mass= 9.10938356×10⁻³¹ Kg
It was discovered by j. j. Thomson in 1897 during the study of cathode ray properties.
How electrons produce the colored light:
Excitation:
When the energy is provided to the atom the electrons by absorbing the energy jump to the higher energy levels. This process is called excitation. The amount of energy absorbed by the electron is exactly equal to the energy difference of orbits.
De-excitation:
When the excited electron fall back to the lower energy levels the energy is released in the form of radiations. this energy is exactly equal to the energy difference between the orbits. The characteristics bright colors are due to the these emitted radiations. These emitted radiations can be seen if they are fall in the visible region of spectrum.
Other process may involve,
Fluorescence:
In fluorescence the energy is absorbed by the electron having shorter wavelength and high energy usually of U.V region. The process of absorbing the light occur in a very short period of time i.e. 10 ∧-15 sec. During the fluorescence the spin of electron not changed.
The electron is then de-excited by emitting the light in visible and IR region. This process of de-excitation occur in a time period of 10∧-9 sec.
Phosphorescence:
In phosphorescence the electron also goes to the excitation to the higher level by absorbing the U.V radiations. In case of Phosphorescence the transition back to the lower energy level occur very slowly and the spin pf electron also change.
Answer:
c 18.0ml
Explanation:
The average mass of one H2O molecule is 18.02 amu. The number of atoms is an exact number, the number of mole is an exact number; they do not affect the number of significant figures. The average mass of one mole of H2O is 18.02 grams. This is stated: the molar mass of water is 18.02 g/mol.
The correct answer is:
TRIGONAL PYRAMIDAL
Answer:
The approximate molar mass of lauryl alcohol is 174.08 g/m
Explanation:
An excersise to apply the colligative property of Freezing-point depression.
This is the formula: ΔT = Kf . m
First of all, think the T° of fusion of benzene → 5.5°C
ΔT = T° pure solvent - T° fusion solution
Kf for benzene: 5.12 °C/m
5.5°C - 4.5°C = 5.12 °C /m . m
1°C / 5.12 m /°C = m
0.195 m = molality
This moles of lauryl alcohol, solute, are in 1 kg of benzene, solvent.
I have to find out in 0.2 kg.
1 kg sv ____ 0.195 moles solute
0.2 kg sv ____ (0.195 . 0.2)/1 = 0.039 moles solute
The mass for these moles is 6.80 g, so if I want to know the molar mass, I have to divide mass / moles
6.80 g/ 0.039 moles = 174.08 g/m
Answer: Thus ∆H, in kJ/mol, for the dissolution of MgSO₄ is -66.7 kJ
Explanation:
To calculate the entalpy, we use the equation:
where,
q = heat absorbed by water = ?
m = mass of water = 
c = heat capacity of water = 4.186 J/g°C
= change in temperature = 
Sign convention of heat:
When heat is absorbed, the sign of heat is taken to be positive and when heat is released, the sign of heat is taken to be negative.
The heat absorbed by water will be equal to heat released by 
To calculate the number of moles, we use the equation:
Given mass = 5.11 g
Molar mass = 120 g/mol
Putting values in above equation, we get:
0.042 moles of releases = 2.8033 kJ
1 mole of releases = 
Thus ∆H, in kJ/mol, for the dissolution of MgSO₄ is -66.7 kJ
