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densk [106]
3 years ago
15

How many grams of ethylene glycol (c2h6o2) must be added to 1.00 kg of water to produce a solution that freezes at -5.00oc? (kf

= 1.86 oc/m)?
Chemistry
1 answer:
leonid [27]3 years ago
6 0

Answer: 167 g


Explanation:


1) The depression of the freezing point of a solution is a colligative property ruled by this equation:


ΔTf = i × m × Kf


Where:


ΔTf is the decrease of the freezing point of the solvent due to the presence of the solute.


i is the Van't Hoof factor and is equal to the number of ions per each mole of solute. It is only valid for ionic compounds. Here the solute is not ionice, so you take i = 1


Kf is the molal freezing constant and is different for each solvent. For water it is 1.86 m/°C


2) Calculate the molality (m) of the solution


ΔTf = i × m × Kf ⇒ m = ΔTf / ( i × Kf) = 5.00°C / 1.86°C/m = 2.69 m


3) Calculate the number of moles from the molality definition


m = moles of solute / kg of solvent ⇒ moles of solute = m × kg of solvent


moles of solute = 2.69 m × 1.00 kg = 2.69 moles


4) Convert moles to grams using the molar mass


molar mass of C₂H₆O₂ = 62.07 g/mol


mass in grams = number of moles × molar mass = 2.69 moles × 62.07 g/mol = 166.97 g ≈ 167 g

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Now we <u>calculate how many moles of water are produced</u>, using the <em>number of moles of the limiting reactant</em>:

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Visual representation of covalent bonding indicating the valence shell electrons in the molecule, lines represents the shared pair of electron and pair of electrons that are not involved in bonding are represented as dots(lone pairs) are known as Lewis structures.

Compound formation takes place in order to complete the octet of each element that is according to octet rule, each atom forms bond with other atom in order to complete their octet that is to get eight electrons in its valence shell and attain stability.

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The number of valence electrons in C_2H_2O = 2\times 4+2\times 1+1\times 6 =16

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