When The rate of effusion is inversely proportional to the √molar mass of the substance.
and we have R(He) = 1L / 4.5 min so,
R(He)/R(Cl2) = (molar mass of Cl2/ molar mass of He)^0.5
and when we have the molar mass of Cl2 = 70.9 & the molar mass of He = 4
so by substitution:
(1L/4.5 min)/ R(Cl2) = (70.9 / 4)^0.5
(1L/4.5 min) / R(Cl2) = 4.21
∴R(Cl2) = (1L/4.5 min) / 4.21 = 1L/ (4.5*4.21)min = 1 L / 18.945 min
∴Cl2 will take 18.945 min for 1 L to effuse under identical conditions
it exists as atom or ion but not as sodium molecule. So there is no any sodium sodium bonding between two sodium atoms. Sodium combines with other element or group to form compounds of sodium like sodium chloride ,sodium carbonate ,sodium sulphate etc. Sodium has symbol Na and its atomic no. is 11 .
Moles HCl reacted : 0.0135
<h3>Further explanation</h3>
Molarity shows the number of moles of solute in every 1 liter of solute or mmol in each ml of solution

Where
M = Molarity
n = Number of moles of solute
V = Volume of solution
So to find the number of moles can be expressed as
n = V x M
The volume of HCl 30 cm³=3.10⁻² dm³
Molarity of HCl = 0.45 mol/dm³
so moles HCl reacted :

A triangle has three sides, three vertices, and three angles. The sum of the three interior angles of a triangle is always 180°. The sum of the length of two sides of a triangle is always greater than the length of the third side.