chemistry

I have two Chemistry related questions that were in my AP Chem summer packet.

The first has to do with Stoichiometry.
It says, "Calculate the number of moles, molecules, and atoms in 60.0 g of boron triflouride.
I calculated that there are .885 moles, and 5.33 x 10^23 molecules. But I can't figure out how to convert it to atoms. It says the answer is 2.13 x 10^24, but how do I get that?

the second deals with solutions,
It asks, "What mass of NaCl is present in 10.0 g of water when ÄTfus=.206 (Kf= 1.86 °C/m)
The solution says
.206= 1.86 (x/.100)
x= .0110 7(7 =subscript) x 58.44 g/mol = .647 g NaCl
We never covered this in class last year and I don't really understand the process. Could someone explain this to me?


You did the molecules. Aren't there four atoms in borontrifluoride (BF3) per molecule?

On the heat..

The total heat released is dependent on the moles of salt per kg of solution, times a constant.
Totalheat= heat/m *molality
now molality= moles salt/kgwater
=gramssalt/58.44 /0.010
or
totalheat= heat/m*gramssalt/0.010*58.44
gramssalt= .206/1.86 * 58.44*.010
This is a decimal place off your text answer. The difference is here...problems states 10 grams, or .010kg. Your text work uses .100 kg, or 100 grams.
= 1.86C/m*molessalt/.01

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asked by kelly

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