Answer: 
Explanation:

where,
= boiling point of solution = ?
= boiling point of solvent (X) = 
= freezing point constant = 
m = molality
i = Van't Hoff factor = 1 (for non-electrolyte like urea)
= mass of solute (urea) = 29.82 g
= mass of solvent (X) = 500.0 g
= molar mass of solute (urea) = 60 g/mol
Now put all the given values in the above formula, we get:


Therefore, the freezing point of solution is 
Don’t currently have a calculator with me but just use Avogadros constant (A) 6.02x10^24, in the equation n=N/A. Lower case n being the number of mol and upper case being the number of molecules (given).
Answer: The balanced reaction is:
<span>2 C6H14(g)+ 19 O2(g) → 12 <span>CO2</span>(g)+ 14 H2O(g)
Note: While balancing the chemical reaction, care must be taken that total number atoms (of each type) on both reactant and product side must be same. In present case, there are 12 'C' atoms, 28 'H' atoms and 38 'O' atoms on both reactant and product side. Hence, the reaction is balanced. </span>
Solar- the sun is not always shining, for example at night you can't get any energy from the sun
Wind-it's not always windy
Water- there can be drought
Really the main issue of all three of these is that they are not always available