Question 6: Energy Use (8 points)

Which aqueous solution has the highest boiling point at standard pressure?(1) 1.0 M KC1(aq) (3) 2.0 M KCl(aq)(2) 1.0 M CaC12(aq)

miss Akunina [59]

Answer:

(4) 2.0 M CaCl₂(aq).

Explanation:

Adding solute to water elevates the boiling point.

The elevation in boiling point (ΔTb) can be calculated using the relation:

ΔTb = i.Kb.m,

where, ΔTb is the elevation in boiling point.

i is the van 't Hoff factor.

van 't Hoff factor is the ratio between the actual concentration of particles produced when the substance is dissolved and the concentration of a substance as calculated from its mass. For most non-electrolytes dissolved in water, the van 't Hoff factor is essentially 1.

Kb is the molal elevation constant of water.

m is the molality of the solution.

(1) 1.0 M KCl(aq):

i for KCl = no. of particles produced when the substance is dissolved/no. of original particle = 2/1 = 2.

suppose molarity = molality, m = 1.0 m,

∴ ΔTb for (1.0 M KCl) = i.Kb.m = (2)(Kb)(1.0 m) = 2(Kb).

(2) 2.0 M KCl(aq):

i for KCl = no. of particles produced when the substance is dissolved/no. of original particle = 2/1 = 2.

suppose molarity = molality, m = 2.0 m,

∴ ΔTb for (1.0 M KCl) = i.Kb.m = (2)(Kb)(2.0 m) = 4(Kb).

(3) 1.0 M CaCl₂(aq):

i for CaCl₂ = no. of particles produced when the substance is dissolved/no. of original particle = 3/1 = 3.

suppose molarity = molality, m = 1.0 m,

∴ ΔTb for (1.0 M KCl) = i.Kb.m = (3)(Kb)(1.0 m) = 3(Kb).

(4) 2.0 M CaCl₂(aq):

i for CaCl₂ = no. of particles produced when the substance is dissolved/no. of original particle = 3/1 = 3.

suppose molarity = molality, m = 2.0 m,

∴ ΔTb for (1.0 M KCl) = i.Kb.m = (3)(Kb)(2.0 m) = 6(Kb).

So, the aqueous solution has the highest boiling point at standard pressure is: (4) 2.0 M CaCl₂(aq).

6 0

3 years ago

What is a change in a substance that does not involve the identity of the substance

GenaCL600 [577]

The answer to this would be a physical change. Physical changes are changes that affect the form of a chemical substance, but not the chemical composition itself. Hope this helped!

6 0

3 years ago

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Which of the following molecules experience dipole-dipole forces as its strongest IMF? A) H2 B) SO2 C) NH3 D) CF4 E) BCl3

Xelga [282]

Answer: $NH_3$

Explanation:

a) $H_2$ : This is a non polar covalent compound which are held by weak vanderwaal forces of attraction.

b) $SO_2$ : This is a covalent compound which is polar due to the presence of lone pair of electrons and are held by dipole-dipole forces of attraction.

c) $NH_3$ : These are joined by a special type of dipole dipole attraction called as hydrogen bond. It forms between electronegative nitrogen atom and hydrogen atom and is the strongest interaction.

d) $CF_4$ : This is a covalent compound and is non polar which are held by weak vanderwaal forces of attraction.

e) $BCl_3$ : This is a covalent compound and is non polar which are held by weak vander waal forces of attraction.

5 0

3 years ago

HELPPPPPPPPPPPPPPPPPP

Svetach [21]

Answer:

distance between them , and mass of the objects

Explanation:

the further away a object is the weaker the gyrational pull is, and imagine lifting a anvil above your head, the anvil weight push's down upon you pulling.

4 0

2 years ago

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Which of these is an element? Carbon Carbon dioxide Air Water

DerKrebs [107]

Answer:

carbon

Explanation:

the rest are mixtures/ compounds.

hope this helps! have a great day!

5 0

3 years ago

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