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3 years ago

Juanita dissolves 46 g of MgBr2 (molar mass: 184.11 g/mol) in 0.5 kg of distilled water. What is the molality of the solution?

1 answer:

3 0

Formula: molality, m = n solute / kg solvent

n solute = # of moles of solute = mass(g) / molar mass

Molar mass of Mg Br2 = 184.11 g/mol

m = [46g / 184.11 g/mol] / 0.5 kg = 0.50 mol/kg

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$\Delta T$ = change in temperature = $(T_2-T_1)=(35.75-25.00)=10.75^oC$

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When heat is absorbed by the solution, this means that heat is getting released by the reaction.

Sign convention of heat:

When heat is absorbed, the sign of heat is taken to be positive and when heat is released, the sign of heat is taken to be negative.

For the given chemical reaction:

$2Na(s)+2H_2O(l)\rightarrow NaOH(aq.)+H_2(g)$

When 0.025 moles of sodium is reacted, the heat released by the reaction is 4.52 kJ

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