The main ingredient of automobile antifreeze mixtures is

Options

A. `CH_(2)(OH)CH(OH)CH_(2)(OH)`
B. `C(CH_OH)_(4)`
C. `CH_(2)(OH)CH(OH)CHO`
D. `CH_(2)(OH)CH_(2)(OH)`

Answer

4

Explanation

A familiar application of `DeltaT_(f)`, is the addition of "permanent" antifreeze, mostly ethylene glycol, `(CH_(2)OH)_(2)` to the water in automobile radiator. Because the boiling point of the solution is elevated, addition of a solute as a winter antifreeze also helps protect against loss of the coolant by summer "boil-over"
The amount by which the freezing anf boiling point change depend on the concentration of the ethylene glycol solution. However, the addition of too much EG is counter productive. The freezing point of pure glycol is about `-12^(@)C`. A solution that is mostly glycol would have a somewhat lower freezingpoint due to the persence of water as a solute.
Suppose we graph the `DeltaT_(f)` of `H_(2)O` below `0^(@)C` as glycol is added, and also graph the DeltaT_(f) of glycol below `-12^(@)C` as `H_(2)O` is added. These two curves would intersect at same temperature, indicating the limit of lowering that can occur.
At thses high concentrations, the solutions do not behave ideally, so the temperature could not be accurately predicted by the equations we have interoduced, but the main ideas still apply.
Most antifreeze labels recommened a `50:50` mixture by volume `(f_(p)-34^(@)F, bp 265^(@)F` with a 15 -psi pressure cap on the radiator), and cite the limit of possible protection with a 70:30 mixture by volume of antifreeze: water `(f_(p)-84^(@)F, bp 276^(@)F` with a 15 - psi pressure cap).