Half-life refers to the time taken for half of the atoms in a radioactive substance to decay. Therefore in 1 half-life the 80 mg of substance will reduce to 40 mg. In another half-life it will reduce from 40 mg to 20 mg, then in a third half-life from 20 mg to 10 mg. Therefore the half-life is equal to the total time taken to decay from 80 mg to 10 mg divided by 3:
t(1/2) = 36 hours / 3 = 12 hours.
Answer:
Is this an actual question that you had for school?
Explanation:
The gas is NH₃.
H₂ doesn't dissolve readily in water, SO₂ gives an acidic solution in water.
The solid residue is Fe(OH)₂.
FeSO₄ and Na₂SO₄ are soluble in water.
The answer is C.
Answer:
0.8 mol.
Explanation:
- The balanced equation for the reaction between Al and FeO is represented as:
<em>2Al + 3FeO → 3Fe + Al₂O₃,</em>
It is clear that 2 mol of Al react with 3 mol of FeO to produce 3 mol of Fe and 1 mol of Al₂O₃.
<em><u>Using cross multiplication:</u></em>
2 mol of Al needs → 3 mol of FeO, from stichiometry.
??? mol of Al needs → 1.2 mol of FeO.
∴<em> The no. of moles of Al are needed to react completely with 1.2 mol of FeO </em>= (2 mol)(1.2 mol)/(3 mol) = <em>0.8 mol.</em>
