First we need to calculate the number of moles of FeS
:
number of moles = mass (grams) / molecular mass (g/mol)
number of moles of FeS = 198.2/120 = 1.65 moles
From the chemical reaction we deduce that:
if 4 moles of FeS produces 8 moles of SO
then 1.65 moles of FeS produces X moles of SO
X = (1.65×8)/4 = 3.3 moles of SO
Now we can calculate the mass of SO:
mass (grams) = number of moles × molecular mass (grams/mole)
mass of SO = 3.3×64 = 211.2 g
For this problem we can use half-life formula and radioactive decay formula.
Half-life formula,
t1/2 = ln 2 / λ
where, t1/2 is half-life and λ is radioactive decay constant.
t1/2 = 8.04 days
Hence,
8.04 days = ln 2 / λ
λ = ln 2 / 8.04 days
Radioactive decay law,
Nt = No e∧(-λt)
where, Nt is amount of compound at t time, No is amount of compound at t = 0 time, t is time taken to decay and λ is radioactive decay constant.
Nt = ?
No = 1.53 mg
λ = ln 2 / 8.04 days = 0.693 / 8.04 days
t = 13.0 days
By substituting,
Nt = 1.53 mg e∧((-0.693/8.04 days) x 13.0 days))
Nt = 0.4989 mg = 0.0.499 mg
Hence, mass of remaining sample after 13.0 days = 0.499 mg
The answer is "e"
Answer:
0.576M and 0.655m
Explanation:
<em>...Dissolves 15.0g of styrene (C₈H₈) in 250.mL of a solvent with a density of 0.88g/mL...</em>
<em />
Molarity is defined as moles of solute (Styrene in this case) per liter of solution whereas molality is the moles of solute per kg of solvent. Thus, we need to find the moles of styrene, the volume in liters of the solution and the mass in kg of the solvent as follows:
<em>Moles styrene:</em>
Molar mass C₈H₈:
8C = 12.01g/mol*8 = 96.08g/mol
8H = 1.005g/mol* 8 = 8.04g/mol
96.08g/mol + 8.04g/mol = 104.12g/mol
Moles of 15.0g of styrene are:
15.0g * (1mol / 104.12g) = 0.144 moles of styrene
<em>Liters solution:</em>
250mL * (1L / 1000mL) = 0.250L
<em>kg solvent:</em>
250mL * (0.88g/mL) * (1kg / 1000g) = 0.220kg
Molarity is:
0.144 moles / 0.250L =
<h3>0.576M</h3>
Molality is:
0.144 moles / 0.220kg =
<h3>0.655m</h3>
<span>They are not seen in nature because they are always combined with something to make something else.</span>
