The molality of a solution that was made by dissolving nacl in 1.5 kg of water is 0.40 m. if the molar mass of nacl is 58.44 g/mol, what is the mass of nacl that was dissolved?
0.27 g
23 g
35 g
39 g

Molality is one way of expressing concentration of a solute in a solution. It is expressed as the mole of solute per kilogram of the solvent. To calculate for the mass of the solute in a given solution, we need to calculate first for the number of moles of the substance by the product of the molality and the mass of the solvent. Then, we convert the number of moles into mass by using the molar mass. 

moles NaCl = 0.40 m (1.5 kg water) = 0.6 mol NaCl

mass NaCl = 0.6 mol NaCl ( 58.44 g / mol ) = 35.06 g NaCl

Therefore, the correct answer would be the third option.

icc, international association for cereal chemistry

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.