Kinetic energy remains conserved in an elastic collision.
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Answer: The daughter nucleus produced when 188 Hg undergoes positron emission is gold.
Explanation:
Positron emission: It is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. This is also known as -decay. In this the mass number remains same.
General representation of an element is given as: 
where,
Z represents Atomic number
A represents Mass number
X represents the symbol of an element
The chemical equation for positron emission is represented as:


The Formula of Acetone is

To find the Mass Molar of a compound, you add the Atomic weights of it's atoms.
If you check the Periodic table:
Atomic Weight of Carbone C: 12.0107
Atomic Weight of Hydrogen: 1.00794
Atomic Weight of Oxygen: 15.9994
So, you got:
Total Atomic Weight of Carbone in Acetone: 12.0107 * 3 = 36.0321
Total Atomic Weight of Hydrogen in Acetone: 1.00794 * 6 = 6.04764
Total Atomic Weight of Oxygen in Acetone = 15.9994 * 1 = 15.9994
Now, you add this numbers
36.0321 + 6.04764 + 15.9994 = 58.07914
So, the Molar Mass of Acetone is 58.09714 g/mol
Hope this Helps :D