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.
Answer: Groups of atoms with aligned magnetic poles are called magnetic domains. Each domain contains an enormous number of atoms, yet the domains are too small to be seen with the unaided eye.
Explanation:
(2.32g/cm³) x (1kg/1000g)x(1 000 000 cm³/1m³) = 2320 kg/m³
1 ml= 1 cm³
X rays have a lower frequency than microwaves would be the scientific statement.