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4 years ago

Determine the molecular formula for the unknown if the molecular mass is 60.0 amu and the empirical formula is ch2o.

Chemistry

1 answer:

mezya [45]4 years ago

5 0

Answer:

The molecular formule for this unknow molecule is C2H4O2

Explanation:

The empirical formula is CH2O ( or better said CnH2nOn)

This means there are 3 elements in the formula of this molecule

⇒ Carbon (C) with a Molar mass of 12 g/mole

⇒ Hydrogen (H) with a Molar mass of 1 g/mole

⇒ Oxygen (O) with a Molar mass of 16 g/mole

We can also notice that the amount of hydrogen should 2x the amount of carbon ( also 2x the amount of oxygen).

The mass of the empirical formule = 12g/ mole + 2* 1 g/mole + 16 g/mole = 30 g/mole

To know what number is n in CnH2nOn we should divide the molecular mass by the empirical mass:

60 g/mole / 30g/mole = 2

this means n = 2

and this will give a molecular formule of C2H4O2

We can control this to calculate the molecular mass:

2*12 + 4* 1 + 2*16 = 24 + 4 + 32 = 60 g/mole

The molecular formule for this unknow molecule is C2H4O2

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Answer:

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Explanation:

We are going to define sucrose as solute, water as solvent and the mix of both, the solution.

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$Molarity = M = \frac{1,22 mol solute}{lts solution}$

We can assume as a calculus base, 1 liter of solution. So, in 1 liter of solution we have 1,22 moles of solute:

$1 lts solution * \frac{1,22 moles solute}{lts solution}=1,22 moles solute$

Knowing that the molality (m) is defined as mol of solute/kgs solvent, we have to calculate the mass of solvent on the solution. Remember our calculus base (1 lts of solution). In 1 lts of solution we have 1120 grams of solution.

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$1,22 mol solute*\frac{342 grs solute}{1 mol solute} = 417,24 grs solute$

Now, the mass of solvent is: mass solvent = mass of solution - mass of solute. So, we have: 1120 - 417,24 = 702,76 grs of solvent = 0,70276 Kgs of solvent

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$%(w/w) = \frac{417,24 grs solute}{1120 grs solution} = 37,2%$

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$702,76 grs solvent*\frac{1 mol solvent}{18 grs solvent} = 39,04 moles solvent$

So, we have the moles of solution: 1,22 moles of solute + 39,04 moles of solvent = 40,26 moles of solution

Finally, we have:

$Mol frac solute = \frac{1,22 mol solute}{40,26 mol solution}= 0,03$

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