The ⁴⁰₁₈X is the symbol for ⁴⁰₁₈Ar - atom and it has 18 protons, 18 electrons, and 22 neutrons.
<h3>What is Mass number ?</h3>
Mass number is the sum of the numbers of protons and neutrons present in the nucleus of an atom.
In the given element, ⁴⁰₁₈X, Subscript 18 is the number of proton and is also equal to the number of electron. While supercript 40 is the atomic mass.
The number of neutrons is given by subtracting the proton number from the mass number.
Therefore,
Number of Neutron = Mass Number - Atomic Number
= 40 - 18
= 22 Neutrons
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The formula for specific gravity is:

where
is the density of the substance and
is the density of water.
The density of water,
= 
Substituting the values in above formula we get,


The formula of density is:

The density of mercury is 
The mass of mercury is 
Substituting the values in density formula:


Answer : The molal freezing point depression constant of liquid X is, 
Explanation : Given,
Mass of urea (solute) = 5.90 g
Mass of liquid X (solvent) = 450 g = 0.450 kg
Molar mass of urea = 60 g/mole
Formula used :

where,
= change in freezing point
= freezing point of solution = 
= freezing point of liquid X = 
i = Van't Hoff factor = 1 (for non-electrolyte)
= Molal-freezing-point-depression constant = ?
m = molality
Now put all the given values in this formula, we get


Therefore, the molal freezing point depression constant of liquid X is, 
Answer:
D. Vibrating around fixed positions
Explanation:
It's right on edge
The correct answer would be A) A soccer ball passed between two players because the ball is in motion.