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Alexeev081 [22]
3 years ago
14

A solution was prepared by dissolving 2.2 g of an unknown solute in 16.7 g of CCl4. A thermal analysis was performed for this so

lution and it was found that its initial freezing point was – 28.7°C. A reliable source in the bibliography states that for CCl4, T°f = – 22.9°C, and its freezing point lowering constant is Kf = 29.9°C/m. Calculate the molar mass of the unknown solute.
Chemistry
1 answer:
laila [671]3 years ago
4 0

Answer:

Molar mass of unknown solute is 679 g/mol

Explanation:

Let us assume that the solute is a non-electrolyte.

For a solution with non-electrolyte solute remains dissolved in it -

Depression in freezing point of solution, \Delta T_{f}=K_{f}.m

where, m is molality of solute in solution and K_{f} is cryogenoscopic constant of solvent.

Here \Delta T_{f}=(-22.9^{0}\textrm{C})-(-28.7^{0}\textrm{C})=5.8^{0}\textrm{C}

If molar mass of unknown solute is M g/mol then-

                 m=\frac{\frac{2.2}{M}}{0.0167}mol/kg

So, 5.8^{0}\textrm{C}=29.9^{0}\textrm{C}/(mol/kg)\times \frac{\frac{2.2g}{M}}{0.0167}mol/kg

so, M = 679 g/mol

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Answer: The correct answer is Option 1.

Explanation:

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What is the molecular structure of water? What are the physical and chemical properties of water?
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Water (H
2O) is a polar inorganic compound that is at room temperature a tasteless and odorless liquid, which is nearly colorless apart from an inherent hint of blue. It is by far the most studied chemical compound and is described as the "universal solvent" [18][19] and the "solvent of life".[20] It is the most abundant substance on Earth[21] and the only common substance to exist as a solid, liquid, and gas on Earth's surface.[22] It is also the third most abundant molecule in the universe.[21]

Water (H
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NamesIUPAC name

water, oxidane

Other names

Hydrogen hydroxide (HH or HOH), hydrogen oxide, dihydrogen monoxide (DHMO) (systematic name[1]), hydrogen monoxide, dihydrogen oxide, hydric acid, hydrohydroxic acid, hydroxic acid, hydrol,[2] μ-oxido dihydrogen

Identifiers

CAS Number

7732-18-5 

3D model (JSmol)

Interactive image

Beilstein Reference

3587155ChEBI

CHEBI:15377 

ChEMBL

ChEMBL1098659 

ChemSpider

937 

Gmelin Reference

117

PubChem CID

962

RTECS numberZC0110000UNII

059QF0KO0R 

InChI

InChI=1S/H2O/h1H2 

Key: XLYOFNOQVPJJNP-UHFFFAOYSA-N 

SMILES

O

Properties

Chemical formula

H
2OMolar mass18.01528(33) g/molAppearanceWhite crystalline solid, almost colorless liquid with a hint of blue, colorless gas[3]OdorNoneDensityLiquid:[4]
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0.961893 g/mL at 95 °C
Solid:[5]
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Refractive index (nD)

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Crystal structure

Hexagonal

Point group

C2v

Molecular shape

Bent

Dipole moment

1.8546 D[16]Thermochemistry

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75.375 ± 0.05 J/(mol·K)[17]

Std molar
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69.95 ± 0.03 J/(mol·K)[17]

Std enthalpy of
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−285.83 ± 0.04 kJ/mol[7][17]

Gibbs free energy (ΔfG˚)

−237.24 kJ/mol[7]
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Answer:

Explanation:

In this case we want to know the structures of A (C6H12), B (C6H13Br) and C (C6H14).

A and C reacts with two differents reagents and conditions, however both of them gives the same product.

Let's analyze each reaction.

First, C6H12 has the general formula of an alkene or cycloalkane. However, when we look at the reagents, which are HBr in ROOR, and the final product, we can see that this is an adition reaction where the H and Br were added to a molecule, therefore we can conclude that the initial reactant is an alkene. Now, what happens next? A is reacting with HBr. In general terms when we have an adition of a molecule to a reactant like HBr (Adding electrophyle and nucleophyle) this kind of reactions follows the markonikov's rule that states that the hydrogen will go to the carbon with more hydrogens, and the nucleophyle will go to the carbon with less hydrogen (Atom that can be stabilized with charge). But in this case, we have something else and is the use of the ROOR, this is a peroxide so, instead of follow the markonikov rule, it will do the opposite, the hydrogen to the more substituted carbon and the bromine to the carbon with more hydrogens. This is called the antimarkonikov rule. Picture attached show the possible structure for A. The alkene would have to be the 1-hexene.

Now in the second case we have C, reacting with bromine in light to give also B. C has the formula C6H14 which is the formula for an alkane and once again we are having an adition reaction. In this case, conditions are given to do an adition reaction in an alkane. bromine in presence of light promoves the adition of the bromine to the molecule of alkane. In this case it can go to the carbon with more hydrogen or less hydrogens, but it will prefer the carbon with more hydrogens. In this case would be the terminal hydrogens of the molecules. In this case, it will form product B again. the alkane here would be the hexane. See picture for structures.

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