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likoan [24]
3 years ago
12

Menthol is a crystalline substance with a peppermint taste and odor. When 1.48 g of menthol is dissolved in 25.0 g of cyclohexan

e, the freezing point of the solution is lowered by 7.90 °C. The freezing point and Kf constant for cyclohexane can be found here. Calculate the molar mass of menthol.
Chemistry
1 answer:
pishuonlain [190]3 years ago
4 0

Answer:

Molar mass of menthol is 155.86 g/mol

Explanation:

Let's apply the colligative property of freezing point depression:

ΔT = Kf . m . i

As menthol is an organic compound we assume the i (Van't Hoff factor as non electrolytic, so i = 1)

m = mol /kg (molality)

Kf = Cryoscopic constant, in this case, for cyclohexane

ΔT = T° freezing of pure solvent - T° freezing solution

7.90°C = 20.8°C / m . m . 1

7.90°C / 20.8 m/°C = m

0.380 m = molality

0.380 moles are the moles of solute (menthol) dissolved in 1kg of solvent, but our mass of solvent is 25 g.

Let's convert the g of solvent to kg to work with molality

25 g = 0.025 kg

molal . solvent mass = moles of solute

0.380 mol /kg . 0.025kg = 9.49×10⁻³ moles

Now, we have the moles and the mass of solute. Let's determine the molar mass of menthol (grams / moles)

1.48 g / 9.49×10⁻³ m = 155.86 g/m

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PLEASE HELP
swat32

Answer:

1461.7 g of AgI

Explanation:

We'll begin by writing the balanced equation for the reaction. This is given below:

CaI₂ + 2AgNO₃ —> 2AgI + Ca(NO₃)₂

From the balanced equation above,

1 mole of CaI₂ reacted to produce 2 moles of AgI.

Next, we shall determine the number of mole AgI produced by the reaction of 3.11 moles of CaI₂. This can be obtained as follow:

From the balanced equation above,

1 mole of CaI₂ reacted to produce 2 moles of AgI.

Therefore, 3.11 moles of CaI₂ will react to produce = 3.11 × 2 = 6.22 moles of AgI

Finally, we shall determine the mass of 6.22 moles of AgI. This can be obtained as follow:

Mole of AgI = 6.22 moles

Molar mass of AgI = 108 + 127

= 235 g/mol

Mass of AgI =?

Mass = mole × molar mass

Mass of AgI = 6.22 × 235

Mass of AgI = 1461.7 g

Therefore, 1461.7 g of AgI were obtained from the reaction.

5 0
3 years ago
An analytical chemist is titrating 118.3 mL of a 0.3500 M solution of butanoic acid (HC3H7CO2) with a 0.400 M solution of KOH. T
TEA [102]

Answer:

pH = 12.33

Explanation:

Lets call HA = butanoic acid and A⁻ butanoic acid and its conjugate base butanoate respectively.

The titration reaction is

HA + KOH ---------------------------- A⁻ + H₂O + K⁺

number of moles of HA :   118.3 ml/1000ml/L x 0.3500 mol/L = 0.041 mol HA

number of  moles of OH  : 115.4 mL/1000ml/L x 0.400 mol/L  = 0.046 mol A⁻

therefore the weak acid will be completely consumed and what we have is  the unreacted strong base KOH which will drive the pH of the solution since the contribution of the conjugate base is negligible.

n unreacted KOH = 0.046 - 0.041 = 0.005 mol KOH

pOH = - log (KOH)

M KOH = 0.005 mol / (0.118.3 +0.1154)L = 0.0021 M

pOH = - log (0.0021) = 1.66

pH = 14 - 1.96 = 12.33

Note: It is a mistake to ask for the pH of the <u>acid solutio</u>n since as the above calculation shows we have a basic solution the moment all the acid has been consumed.

4 0
3 years ago
How many grams of ammonia (NH3) can be produced by the synthesis of excess hydrogen gas (H2) and 253.8 grams of nitrogen gas (N2
kogti [31]

Answer:

308.2 g of NH₃.

Explanation:

We'll begin by writing the balanced equation for the reaction. This is illustrated below:

3H₂ + N₂ —> 2NH₃

Next, we shall determine the mass of N₂ that reacted and the mass of NH₃ produced from the balanced equation. This can be obtained as follow:

Molar mass of N₂ = 2 × 14 = 28 g/mol

Mass of N₂ from the balanced equation = 1 × 28 = 28 g

Molar mass of NH₃ = 14 + (3×1)

= 14 + 3 = 17 g/mol

Mass of NH₃ from the balanced equation = 2 × 17 = 34 g

Summary:

From the balanced equation above,

28 g of N₂ reacted to produce 34 g of NH₃.

Finally, we shall determine the mass of NH₃ produced by the reaction of 253.8 g of N₂. This can be obtained as illustrated below:

From the balanced equation above,

28 g of N₂ reacted to produce 34 g of NH₃.

Therefore, 253.8 g of N₂ will react to produce = (253.8 × 34)/28 = 308.2 g of NH₃.

Thus, 308.2 g of NH₃ were obtained from the reaction.

8 0
3 years ago
Fill in the blanks below.
Elenna [48]

Answer:

Explanation:

6CO₂ + 6 H₂O ⇄ C₆H₁₂0₆ + 6O₂

This is the chemical equation given .

1. The equation shows a __Chemical equation_______the breaking and forming of chemical bonds that leads to a change in the composition of matter.

2. In the equation, CO₂ is a___reactant_____.

3. In the equation, C₆H₁₂0₆ is a ___product________.

4. In O₂, the type of bond that holds the two oxygen atoms together is a_nonpolar_covalent bond_________.

5. In H₂O, the type of bond that holds one of the hydrogen atoms to the oxygen atom is a__polar_hydrogen bond____.

6. The number of oxygen atoms on the left side of the equation is__equal to_________ the number of oxygen atoms on the right side.

5 0
3 years ago
Indicate which factors affect the rate of a reaction. select all that apply. temperature δs o keq δg o δh o ea concentration k c
melamori03 [73]
Several factors affect the rate of a chemical reaction. From the options given factors that affect the rate are:
temperature and concentration of catalysts.
As the temperature increases, also the rate of the reaction increases.
<span>The concentration of a catalysts helps a reaction to proceed more quickly to equilibrium. </span>
5 0
3 years ago
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