The molecular formula for compound is
mass of compound is 0.670 g.
To calculate number of atoms first calculate number of moles in the compound as follows:

Molar mass of
is 283.886 g/mol, thus,

Thus, number of mole of
is 0.00236 mol.
From the molecular formula 1 mole of
has 2 mol of P (phosphorus) and 5 mol of O (oxygen).
Thus, number of moles of P and O in 0.00236 mol of
will be:

Similarly,

Now, in 1 mol of an element there are
atoms.
Number of atoms of P will be:

Similarly, number of atoms of O will be:

Total number of atoms will be sum of number of atoms of P and O:

Therefore, total number of atoms in
will be
.
A.)49.4974874 moles or 49.5 moles
B.)2.980808730172671e+25 or 3e+25
Complete Question
The complete question is shown on the first question
Answer:
a) The duty of the heat exchanger is given as 6.8658 KJ /sec
b) The temperature of the water leaving the exchanger is TOUT = 29.84 ⁰C
c) The log mean difference is given as TZ = 47.317 ⁰ C
d) the UA value is UA = 145.10
Explanation:
The explanation is uploaded on the first and second ,third and fourth image
A + BC ---> AB + C
So here one reactant (A) is accepting a group which is being given by another compound (BC) however the A is not giving any group / element or ion
So this single displacement
Similarly in the given reaction
the anion OH- is only being replaced
The element Ca accepts OH- and H2O loses the same group to form new element H2
So the correct answer is
Single replacement also known as single displacement.
The answer would be option 4