Solubility

[DeathandTaxes]

An aqueous solution was prepared by mixing 70 grams of sugar (C12H12O11) into 100 grams of water. The solution has a boiling point of 101.11 and Kb = 0.512, what is the molar mass of the solute?

The answer is 322.58, but I don't understand why we can't just do (12*12 + 12 + 11*16) since they give us the molecular formula.

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[Czarcasm]

An aqueous solution was prepared by mixing 70 grams of sugar (C12H12O11) into 100 grams of water. The solution has a boiling point of 101.11 and Kb = 0.512, what is the molar mass of the solute?

The answer is 322.58, but I don't understand why we can't just do (12*12 + 12 + 11*16) since they give us the molecular formula.

Lol, I thought the same. Stupid question.

 

[Hadi7183]

The main purpose of those extra pieces of information is just to distract you. This is actually a common bait in the MCAT. In this case, it was too obvious that you don't need those information to answer the question, but in more complex questions this trick can easily hunt you.

 

[DeathandTaxes]

Hadi, if you use the molecular formula you actually get something greater than 322. So the extra pieces of information were necessary to solving the problem

This was from Kaplan's General Chemistry review btw.

 

[DrknoSDN]

Hadi, if you use the molecular formula you actually get something greater than 322.

... How do you figure?

12*12 = 144
16*11 = 176
1*12=12
144+176+12=332.