Hello!
Ok so for this problem we use the ideal gas law of PV=nRT and I take it that the scientist needs to store 0.400 moles of gas and not miles.
So if we have
n=0.400mol
V=0.200L
T= 23degC= 273k+23c=296k
R=ideal gas constant= 0.0821 L*atm/mol*k
So now we rearrange equation for pressure(P)
P=nRT/V
P=((0.400mol)*(0.0821 L*atm/mol*k)*(296k))/(0.200L) = 48.6 atm of pressure
Hope this helps you understand the concept and how to solve yourself in the future!! Any questions, please feel free to ask!! Thank you kindly!!!
HCH bond angle is ~110 degrees.
The mass of 63 ml sample : 79.38 g
<h3>Further explanation</h3>
Given
20 ml and 25.2 g of glycerol
Required
The mass of 63 ml sample
Solution
Density is the ratio of mass per unit volume
Density formula:

Density of glycerol :
= m : V
= 25.2 g : 20 ml
= 1.26 g/ml
Mass of 63 ml sample :
= density x volume
= 1.26 g/ml x 63 ml
= 79.38 g
The most abundant is 35/17 Cl
explanation
This is because Chlorine 35/17 is the one close to the average atomic mass of chlorine which is 35.46 u making it to be the most abundant.
average atomic mass of chlorine is 35.46 + or- 0.02