When 5.42 g of a certain molecular compound x are dissolved in 80.0 g of formamide (nh, coh), the freezing point of the solution is measured to be -1.4 °c. calculate the molar mass of x. if you need any additional information on formamide, use only what you find in the aleks data resource. also, be sure your answer has a unit symbol, and is rounded to 2 significant digits. one x 6 ?

Molecular mass of X is 73g/mol

Explanation:

To answer this question you need to know that Freezing-point depression (A colligative property) is the decrease of the freezing point of a solvent on the addition of a non-volatile solute. The formula is:

ΔT = Kf m

Where ΔT is the freezing point depression (2,57°C - (-1,4°C) =  3,97°C Where 2,57°C is the melting point of formamide.

Kf that is freezing point molar constant of the solvent (4,25°C/m)

And m that is molality (moles of solute/kg of solvent). Replacing:

m =

Knowing you have 80,0g of solvent ≡ 0,0800 kg:

0,934 mol solute/kg solvent×0,08 kg solvent = 0,07472 moles of solute ≡ moles X

As grams of X are 5,42, molecular mass of X is:

=  73 g/mol

I hope it helps!

Answer : The molar mass of X is 72 g/mol.

Explanation :  Given,

Mass of X (solute) = 5.42 g

Mass of formamide (solvent) = 80.0 g  = 0.080 kg

Molar mass of formamide = 45.04 g/mole

Formula used :  

where,

= change in freezing point

= freezing point of solution =

= freezing point of formamide =

i = Van't Hoff factor = 1  (for no-electrolyte)

= freezing point constant for formamide =

m = molality

Now put all the given values in this formula, we get

Therefore, the molar mass of X is 72 g/mol.

i'm assuming that the correct answer is indeed the first one/ "a"..