Before you begin titration, drops of indicator are added to the Erlenmeyer flask. This happens when preparing to measure pH change.
<u>Answer:</u> The spacing between the crystal planes is 
<u>Explanation:</u>
To calculate the spacing between the crystal planes, we use the equation given by Bragg, which is:

where,
n = order of diffraction = 2
= wavelength of the light =
(Conversion factor:
)
d = spacing between the crystal planes = ?
= angle of diffraction = 22.20°
Putting values in above equation, we get:

Hence, the spacing between the crystal planes is 
Add the Pressure of neon and argon that is 0.68 +0.35= 1.03
Total pressure that is 1.25 -1.03=0.22 atm