in example is in the cooling system of a car
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density = mass / volume
if you know the mass of the sample and the volume, you can determine density and then concentration
"Ethylene glycol is the most widely used automotive cooling-system antifreeze, although methanol, ethanol, isopropyl alcohol, and propylene glycol are also used"
the density of the most common antifreeze = 1.123g/ml
this means that for every 1ml of solution, it has a mass of 1.123g.
molality = moles solute / kg solvent
the molar mass of polyethylene glycol = 92835 g/mole
1ml water = 1g water = 0.001kg water
1.123g / 92835g/mole = 1.21x10^-5moles PEG
1.21x10^-5moles / 0.001kg = 0.0121molal
or
1.21x10^-5moles / 1ml = 1.21x10^-5moles / 0.001L = 0.0121M
if you know the mass of the sample and the volume, you can determine density and then concentration
"Ethylene glycol is the most widely used automotive cooling-system antifreeze, although methanol, ethanol, isopropyl alcohol, and propylene glycol are also used"
the density of the most common antifreeze = 1.123g/ml
this means that for every 1ml of solution, it has a mass of 1.123g.
molality = moles solute / kg solvent
the molar mass of polyethylene glycol = 92835 g/mole
1ml water = 1g water = 0.001kg water
1.123g / 92835g/mole = 1.21x10^-5moles PEG
1.21x10^-5moles / 0.001kg = 0.0121molal
or
1.21x10^-5moles / 1ml = 1.21x10^-5moles / 0.001L = 0.0121M
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The main instrument is a hydrometer, which can also check the density of the sulphuric acid in a battery. It can give a good indication of the % of alcohol in making wine., and of giving a good indication of the antifreeze. The more dense the less it sinks in.