Electron affinity is a measure of the tendency of a neutral atom to gain electrons and form a negative ion. It can be represented by a general equation:
X + e- → X-
The value of electron affinity decreases on moving down a group. This is because on moving down a group the atomic size increases as a result the added electron feels less pull or attraction towards the nucleus.
In group 14, Carbon 'C' is the first member and therefore will have the highest electron affinity.
Ans : A) Carbon
Concentration is the number of moles of solute in a fixed volume of solution
Concentration(c) = number of moles of solute(n) / volume of solution (v)
25.0 mL of water is added to 125 mL of a 0.150 M LiOH solution and solution becomes more diluted.
original solution molarity - 0.150 M
number of moles of LiOH in 1 L - 0.150 mol
number of LiOH moles in 0.125 L - 0.150 mol/ L x 0.125 L = 0.01875 mol
when 25.0 mL is added the number of moles of LiOH will remain constant but volume of the solution increases
new volume - 125 mL + 25 mL = 150 mL
therefore new molarity is
c = 0.01875 mol / 0.150 L = 0.125 M
answer is 0.125 M
Absorbance is related to the concentration of a substance using the Beer-Lambert's Law. According to this law, absorbance is linearly related to concentration. However, this is only true up to a certain concentration depending on the substance. For this case, we assume that the said law is applicable.
A = kC
Using the first conditions, ewe solve for k.
0.26 = k (0.10)
k = 2.6
A = kC
A = 2.6 (0.20) = 0.52
Therefore, the absorbance at a concentration of 0.20 M and wavelength of 500nm is 0.52.
When we say decrease in boiling point, that means, we achieve boiling at a more lower temperature (lower than 100deg C). This is due to the lower atmospheric pressure. Boiling happens when the vapor pressure is equal the atmospheric pressure. Lower atmospheric pressure takes lower temperature for vapor pressure to equate with the atmospheric pressure. The answer here is letter B.
At higher elevations, it would take longer to hard boil an egg, because there is a lower boiling point, so the egg is boiling in water at a lower temperature.
First step is to get the mass of the mercury:
Pressure = mass/volume
mass = pressure x volume = 13.5 x 1.85 = 24.975 gm
Second step is to calculate the number of moles in 24.975 gm:
From the periodic table, the molar mass of mercury is 200.59
mass = number of moles x molar mass
number of moles = 24.975 / 200.59 = 0.1245 mole
Last step is to get the number of atoms:
Each mole contains 6.02 x 10^23 atoms
number of atoms = 0.1245 x 6.02 x 10^23 = 7.4949 x 10^22 atoms
