How can I prepare a 25 degree brix 100ml solution with sucrose?

[miniradman]

Hello there, I'm learning how to make wine in my Chemistry class and the first task we had to do is prepare a 100ml solution with a 25% sucrose content. However, I don't know where to begin. I know that 25 grams of sugar plus 75 grams of water will not add up to 100mls of solution.

I've done something like this before with volume contraction of ethanol and water and remember something about density? Well the density of sucrose is $1.59g/cm^{2}$ and water is going to be assumed to be $1 g/cm^{2}$ (because we are using tap water)

How do I approach this?

thank you - miniradman

 

[HallsofIvy]

"25% solution" by what? You can prepare concentrations by volume, mass, number of molecules and they all are different.

You talk about the mass density of sucrose so I suppose you mean by mass or weight. To have a 25% solution (.25= 1/4), you must have three times the mass of water as sucrose. If, for example, you have 1 kg of sucrose, you must dissolve it in 3 kg of water to have a total mass of 4 kg. so that the sucrose is 1 kg/4kg= 1/4= 25% of the whole mass. You need the density of sucrose only if you are measuring it by volume. Of course, for water, at standard temperature and pressure, 1 g mass is equal to 1 cm volume.

 

[miniradman]

yes, but if I put 25 grams of sugar, and 75 grams of water, it will not give me a 100ml solution due to the differences in intermolecular forces, and the sheer size of the sucrose molecule in comparision to the water molecule?

 

[Borek]

You need an exact density of the 25% w/w sucrose solution (take it from density tables) - that will let you calculate mass of 100 mL of the solution. Once you know that calculating masses of sucrose and water is a breeze.

 

[miniradman]

is there any way I can find the weight needed using mathematical calculations over pre-made tables?

 

[Borek]

No.

˙