A calcium atom has 20 protons!
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Answer:
If the volume is doubled and the number of molecules is doubled, pressure is unchanged
Explanation:
Step 1: Data given
Temperature = constant
Volume will be doubled
Number of molecules will be doubles
Step 2:
p*V = n*R*T
⇒ gas constant and temperature are constant
Initial pressure = n*R*T / V
Initial pressure = 2*R*T/2
Initial pressure = RT
Final pressure = 4*RT / 4
Final pressure = R*T
If the volume is doubled and the number of molecules is doubled, pressure is unchanged
Answer : The correct option is, (B) 
Solution :
According to the Graham's law, the rate of effusion of gas is inversely proportional to the square root of the molar mass of gas.

or,
..........(1)
where,
= rate of effusion of unknown gas = 
= rate of effusion of oxygen gas = 
= molar mass of unknown gas = ?
= molar mass of oxygen gas = 32 g/mole
Now put all the given values in the above formula 1, we get:


The unknown gas could be carbon dioxide
that has approximately 44 g/mole of molar mass.
Thus, the unknown gas could be carbon dioxide 
Answer:
recording the wavelength of light
Explanation:
When an appropriate measure of energy say in the form of light of a certain wavelength, is supplied, electrons have a tendency to absorb the energy and get excited to a higher energy level. Conversely, if an electron is already at a higher energy state it will emit energy in the form of light (or heat) and return to a more stable lower energy state.