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# Molality and Molarity Questions

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Question #1: For the reaction:
2 Al + 6 HBr (aq) ---> 3H2 + 2 AlBr3
What volume of 0.300 M HBr(aq) is needed to react with 22.6 g of AL?

Question #2: The density of a 3.92 M solution of NaCl in water is 1.148 g/cm^3 at 20 degrees celcius. Find the molality (not molarity) of this solution.

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#### Solution Preview

Q 1: 1 mole of HBr == 79.9+1 = 80.9 gm
1 mole of Al == 26.98 gm

2 moles of Al == 6 moles of HBr
=> 2*26.98 gm Al == 6 moles of HBr
=> 22.6 gm Al == 6*22.6/(2*26.98) = 2.513 mole of HBr

0.3M ...

#### Solution Summary

A question is solved to find volume of a solution of given molarity while reacting with the other element of given quantity. The other problem solves for estimating molality of given solution.

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