Volume = nRT/P
n = number of particles (moles)
R = universal gas constant (0.0821)
T = temperature (Kelvin)
P = pressure (atm)
(Assuming you have 1 mole of Helium in a chemical reaction) We would need to convert grams to moles: 12.0g He x 1 mol He/4 molar mass of He = 3 mol He
Convert Celsius to Kelvin: 100*C + 273.15 = 373.15 K
Now we can set up the equation for volume: (3mol)(0.0821)(373.15)/1.2atm = 76.6 L of Helium gas
Electrons, specifically valence electrons
Atomic mass silicon = 28.085 u
1 mol Si ---------------- 28.085 g
? ------------------------ 245 g
245 x 1 / 28.085 => 8.72 mol
answer A
Since Au is a symbol for Gold, and once you split the name into to giving each ion its charge... you'll see that this compound has Au+2 and Cl03- .... so the name would be
Gold(II) Chlorate
Hope this helps!