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slamgirl [31]
3 years ago
11

Calculate the molality for each of the following solutions. Then, calculate the freezing-point depression ΔTF = iKFcm produced b

y each of the salts. (Assume the density of water is 1.00 g/mL and KF = 1.86°C/m.) (a) 3.2 M NaCl (Assume the density of the solution is 1.00 g/mL.) Cm = WebAssign will check your answer for the correct number of significant figures. 3.9 Correct: Your answer is correct. m ΔTF = WebAssign will check your answer for the correct number of significant figures.14.5 Incorrect: Your answer is incorrect. Check the number of significant figures.°C (b) 24 g of KCl in 1.5 L of water Cm = WebAssign will check your answer for the correct number of significant figures. 0.21 Correct: Your answer is correct. m ΔTF = WebAssign will check your answer for the correct number of significant figures. 0.78 Incorrect: Your answer is incorrect. °C
Chemistry
1 answer:
zlopas [31]3 years ago
7 0

Answer:

a) Cm= 3.9 m  ; ΔTf= 14.51 ºC

b) Cm= 0.21 m ; ΔTf= 0.79ºC

Explanation:

In order to solve the problems, we have to remember that the molality (m) of a solution is equal to moles of solute in 1 kg of solvent.

m= mol solute/kg solvent

a) In this case we have molarity, which is moles of solute in 1 liter of solution. We have to know how many kg of solvent (water) we have in 1 L of solution.

3.2 M NaCl= 3.2 mol NaCl/ 1 L solution

1 L solution= 1000 ml solution x 1.00 g/ml= 1000 g

A solution is composed by solute (NaCl) + solvent, so:

1000 g solution = g NaCl + g solvent

g NaCl= 3.2 mol NaCl x 58.44 g/mol= 187 g NaCl

g solvent= 1000 g - 187 g NaCl= 813 g= 0.813 kg

Cm= 3.2 g NaCl/0.813 kg solvent= 3.9 m

NaCl is an electrolyte and it dissociates in water in two ions: Na⁺ anc Cl⁻, si the van't Hoff factor (i) is 2.

ΔTf= i x KF x Cm= 2 x 1.86ºC/m x 3.9 m= 14.51ºC

b) In this case we have 24 g of solute in 1.5 L of solvent. We have to convert the liters of solvent to kg, and to convert the mass of solute to mol by using the molecular weight of KCl (74.55 g/mol):

24 g KCl x 1 mol KCl/74.55 g= 0.32 mol

1.5 L solvent= 1500 g solvent x 1.00 g/ml= 1500 g = 1.5 kg

Cm= 0.32 g KCl/1.5 kg solvent= 0.21 m

KCl is an electrolyte and when it dissolves in water, it dissociates in 2 ions: K⁺ and Cl⁻. For this, van't Hoff factor (i) is equal to 2.

ΔTf= i x KF x Cm= 2 x 1.86ºC x 0.21 m= 0.79ºC

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Alex777 [14]

The question is incomplete, the complete question is:

Nitrogen and fluorine react to form nitrogen fluoride according to the chemical equation:

N_2(g)+3F_2(g)\rightarrow 2NF_3(g)

A sample contains 19.3 g of N_2 is reacted with 19.3 g of F_2. Now we need to find the amount of NF_3 that can be formed by the complete reactions of each of the reactants.

If all of the N_2 was used up in the reaction, how many moles of NF_3 would be produced?

<u>Answer:</u> 1.378 moles of NF_3 are produced in the reaction.

<u>Explanation:</u>

The number of moles is defined as the ratio of the mass of a substance to its molar mass.

\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}       ......(1)

Limiting reagent is defined as the reagent which is completely consumed in the reaction and limits the formation of the product.

Excess reagent is defined as the reagent which is left behind after the completion of the reaction.

In the given chemical reaction, N_2 is considered as a limiting reagent because it limits the formation of the product and it was completely consumed in the reaction.

We are given:

Mass of N_2 = 19.3 g

Molar mass of N_2 = 28.02 g/mol

Putting values in equation 1:

\text{Moles of }N_2=\frac{19.3g}{28.02g/mol}=0.689mol

For the given chemical reaction:

N_2(g)+3F_2(g)\rightarrow 2NF_3(g)

By the stoichiometry of the reaction:

1 mole of N_2 produces 2 moles of NF_3

So, 0.689 moles of N_2 will produce = \frac{2}{1}\times 0.689=1.378mol of NF_3

Hence, 1.378 moles of NF_3 are produced in the reaction.

8 0
3 years ago
Why is sodium chloride not considered a molecular compound? What kind of compound is it?
e-lub [12.9K]

Answer:

Something like table salt (NaCl) is a compound because it is made from more than one kind of element (sodium and chlorine), but it is not a molecule because the bond that holds NaCl together is an ionic bond. If you like, you can say that sodium chloride is an ionic compound.

Explanation:

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2 years ago
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Compound formula is C₉H₈O₄
the molar masses of the atoms making up the compound 
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Answer:

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Answer:

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Now we apply the C1V1 = C2V2 equation using the concentration and volume of Na2CO3 because it's molar ratio is one to one to NaCl (You can also use HCL, but you have to divide their moles by 2 for the molar ratio)  and the volume we just calculated for NaCl.

(0.75M) x (0.094L) = C2 x (0.329L)

Rearrange equation to solve for C2:

<u>(0.75M) x (0.094L)</u>  =  C2

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C2 = 0.214 M (Rounded)

<u>When the reaction is finished, the NaCl solution will have a molarity concentration of 0.214 M.</u>

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7 0
2 years ago
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