Answer: 8.1 days
Explanation:
Expression for rate law for first order kinetics is given by:
where,
k = rate constant
t = age of sample
a = let initial amount of the reactant = x
a - x = amount left after decay process= 
a) to find rate constant
Half life is the amount of time taken by a radioactive material to decay to half of its original value.
b) for completion of one fourth of reaction
Thus after 8.1 days , one fourth of original amount will remain.
7 protons means that N atom has 7 electrons
1st level can have only 2 e⁻, and we have left over of 7-2=5 e⁻, that will go on the second level.
B. 2,5
Molar mass of copper chloride is 134.45 g/mole, so the mole of 10.5 g copper chloride is 10.5/134.45 = 0.078 mole. Molar mass of aluminum is 27 g/mole, so the mole of 12.4 g aluminium is 12.4/27 = 0.46 mole. The formula of this reaction is as follows, 2Al + 3CuCl2 ⇒ 2AlCl3 + 3Cu. Thus the molar ratio of the reactants is Al:CuCl2 = 2:3. So to react with 0.078 mole of copper chloride, will need 0.078 x 2/3 = 0.052 moles of aluminum which is less than the given amount (0.46mole). Therefore, copper chloride is the limiting reactant.
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