Given the mass of
=25.6 g
The molar mass of
=390.35g/mol
Conversion of mass of
to moles:

Conversion of moles
to moles of sulfur:

Conversion of moles of sulfur to individual sulfur atoms using Avogadro's number:
1 mol = 

Initially, we calculate the moles of gas using the ideal gas law:
PV = nRT
n = PV / RT
n = (1.4 * 226.4) / (0.082 *(27 + 273.15))
n = 12.88
Next, we apply the given percentages to estimate the moles of helium:
Moles of helium = 0.655 * 12.88
Moles of helium = 8.44
We then use the formula:
Mass = moles * molar mass
Mass of helium = 8.44 * 4
Mass of helium = 33.76 grams.
Answer:
Endothermic: water formation from ice and a cold instant ice pack Explanation: