There are 30 protons and 39 neutrons in the nucleus.
This must me the isotope of an element with an atomic mass close to 69 u.
The only candidates are Zn and Ga.
Zn has a zinc-69 isotope with mass 68.926 u.
Ga has a gallium -69 isotope with mass 68.925 u.
The isotope is probably

.
It has 30 protons and 39 neutrons.
Answer: The molecular mass of this compound is 131 g/mol
Explanation:
Depression in freezing point:
where,
= depression in freezing point =
= freezing point constant = 
m = molality
i = Van't Hoff factor = 1 (for non-electrolyte)
= mass of solute = 0.49 g
= mass of solvent (cyclohexane) = 20.00 g
= molar mass of solute = ?
Now put all the given values in the above formula, we get:
Therefore, the molar mass of solute is 131 g/mol
add up the mass of protons and neutrons
Answer:
0.0400M of KI
Explanation:
Molarity is an unit of concentration defined as the ratio between moles of solute and liters of solution.
When you add 10.0 mL of 0.10M KI and 15.0mL, total volume is:
25.0mL = <em>0.025L of solution</em>
<em />
And moles of KI are:
0.0100L × 0.10M = <em>0.00100 moles of KI</em>
<em />
Thus, molarity is:
0.00100 moles / 0.025L = <em>0.0400M of KI</em>