Answer:
13 years
Explanation:
From;
0.693/t1/2 = 2.303/t log (No/N)
Where;
t1/12 = half-life of Cobalt-60 = 5.3 years
t = time taken = the unknown
No = mass of radioactive material originally present = 5.2 g
N = mass of radioactive material at time t = 0.95 g
Substituting values;
0.693/5.3 = 2.303/t log (5.2/0.95)
0.131 = 2.303/t(0.738)
0.131 = 1.6996/t
t = 1.6996/0.131
t = 12.97 years
t = 13 years(to the nearest whole number)
Answer:
6.79 g of phosphine can be produced
Explanation:
The reaction is this:
3H₂ + 2P → 2PH₃
We have the mass of the two reactants, so let's find out the limiting reactant, so we can work with the equation. Firstly, we convert the mass to moles (mass / molar mass)
6.2 g / 30.97 g/mol = 0.200 moles of P
4g / 2 g/mol = 2 moles of H₂
Ratio is 3:2.
3 moles of hydrogen react with 2 moles of P
Then, 2 moles of H₂ would react with (2 . 2)/ 3 = 1.3 moles of P.
We have only 0.2 moles of P, so clearly the phosphorous is the limiting reactant.
Ratio is 2:2. So 2 moles of P can produce 2 moles of phosphine. Therefore, 0.2 moles of P must produce the same amount of phosphine.
Let's convert the moles to mass ( mol . molar mass)
0.2 mol . 33.97 g/mol = 6.79 g
Atomic number is number on periodic table, mass is how big element is
