Explanation:
Reaction equation showing alpha decay in Uranium-238 is as follows.

It is known that an alpha particle is basically a helium nucleus and it contains 2 protons and 2 neutrons.
Symbol of an alpha particle is
.
As atomic mass or weight is the sum of total number of protons and neutrons present in an atom.
Hence, the atomic weight of the alpha particle is (2 + 2) = 4.
Complete Question
The complete question is shown on the first uploaded image
Answer:
The partial pressure is
Explanation:
The Partial pressure of
is mathematically represented as

Where
is the total pressure of water with a value of 15.5 mm of Hg
is the partial pressure of water with a value 753 mm of Hg
Now substituting values

Answer:
Number of moles = 3.73 mol
Explanation:
Given data:
Mass of LiCl = 158 g
Number of moles = ?
Solution:
Formula:
Number of moles = mass/ molar mass
Molar mass of LiCl = 42.4 g/mol
Number of moles = 158 g / 42.4 g/mol
Number of moles = 3.73 mol