You will want to find how many grams are in a whole mole so you know which element it is. To do this, find out how much of a mole you have.
4.95 x 10^23 atoms / 6.022 x 10^23 atoms (one whole mole of any element) = .8219860511 or ~82% of 1 mole
Now we know that, find what to multiply 20 g by to get the rest of the mole.
1 mole / .8219860511 mole = 1.216565657
20 g x 1.216565657 = ~24.33 g / mol
Now that you have grams per mole, you can look at the periodic table and the molar masses to see which this number is closely aligned.
Your answer is Magnesium (Mg), which has a molar mass of 24.305 g
Answer:
73.88 g/mol
Explanation:
For this question we have to keep in mind that the unknown substance is a <u>gas</u>, therefore we can use the <u>ideal gas law</u>:

In this case we will have:
P= 1 atm
V= 3.16 L
T = 32 ªC = 305.15 ºK
R= 0.082 
n= ?
So, we can <u>solve for "n"</u> (moles):



Now, we have to remember that the <u>molar mass value has "g/mol"</u> units. We already have the grams (9.33 g), so we have to <u>divide</u> by the moles:


Answer:
fH = - 3,255.7 kJ/mol
Explanation:
Because the bomb calorimeter is adiabatic (q =0), there'is no heat inside or outside it, so the heat flow from the combustion plus the heat flow of the system (bomb, water, and the contents) must be 0.
Qsystem + Qcombustion = 0
Qsystem = heat capacity*ΔT
10000*(25.000 - 20.826) + Qc = 0
Qcombustion = - 41,740 J = - 41.74 kJ
So, the enthaply of formation of benzene (fH) at 298.15 K (25.000 ºC) is the heat of the combustion, divided by the number of moles of it. The molar mass od benzene is: 6x12 g/mol of C + 6x1 g/mol of H = 78 g/mol, and:
n = mass/molar mass = 1/ 78
n = 0.01282 mol
fH = -41.74/0.01282
fH = - 3,255.7 kJ/mol
(ANS1)— P4 + 5O2 ---> 2P2O5
(ANS2)— C3H8 + 5O2---> 3CO2 + 4H20
(ANS3)— Ca2Si + 4Cl2 ---> 2CaCl2 + SiCl4