STP stands for the Standard Temperature and Pressure. The standard temperature is 273 Kelvin or 0 degrees Celcius or 32 Fahrenheit and the standard pressure is 1 atm pressure or 760 mmHg, or 10,325 Pascals. STP is most commonly used when performing calculations on gases.
142 g ---------------- 6.02 x 10²³ molecules
0.920g g ------------ ( molecules )
molecules = 0.920 x ( 6.02 x 10²³ ) / 142
molecules = 5.53 x 10²³ / 142
= 3.89 x 10²¹ molecules
1 molecule P2O5 -------------------------- 7 atoms
3.89 x 10²¹ molecules -------------------- ( atoms )
atoms = ( 3.89 x 10²¹) x 7 / 1
atoms = <span>2.72 x 10²² atoms of P2O5
Hope this helps!!!
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Each element or compound has a molar mass, which is calculated by multiplying the atomic mass of each element by the amount of atoms of that element, and summing the results of each element. The molar mass is measured in g/mol. So you divide the mass in grams by the molar mass to get the amount of moles.
Example:
There are 5g of water.
Calculate the amount of moles.
The water's formula is H2O, so the molar mass of it is

g/mol.
The amount of moles is:
5g ÷ 18g/mol ~ 0.28mol