Quinine is a natural product extracted from the bark of the cinchona tree, which is native to south america. quinine is used as an antimalarial agent. when 1.53 g of quinine is dissolved in 25.0 g of cyclohexane, the freezing point of the solution is lowered by 3.93 °c. the freezing point and kf constant for cyclohexane can be found here. calculate the molar mass of quinine.

The formula for freezing point depression is: ΔTf = mkfi 

Where:
kf = freezing point constant 
i = Van't Hoff factor which in this case is 1 
m = molality (moles of solute/kg of solvent) 
ΔTf = temperature change 

ΔTf is 3.93°C, the molality is the amount of solute Quinine in the solvent cyclohexane. Moles cannot be calculated, therefore substitution of moles with g/mm is needed.
moles is g/m, therefore molality is equal to (g/mm)/kg 

Calculations:

molality = (0.153/mm)/0.025 = 6.12/mm 

3.93 = 6.12/mm(20.8)

mm = (6.12/3.93)(20.8) = 32.39 g/mol

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.

on passing the small ampere of electric current through the tube made of ar and hg of cfl generates uv rays which excites the fluorescent and thus emits the high radiation by consumption of just 5- 12 w in comparison to incandescent light which requires more power such as around 40 - 55 w to lighten.

moreover the life span of fluorescent or cfl is around 8000 h whereas the life span of incandescent is around 1200 h

hence, the building installed with incandescent lights bears more electricity bill.