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lutik1710 [3]
3 years ago
14

When 1.04 g of an unknown non-electrolyte is dissolved in 50.0 g of cyclohexane, the freezing point decreased by 3.91 degrees C.

If the Kfp of the solvent is 20.1 K/m, calculate the molar mass of the unknown solute.
Chemistry
1 answer:
Advocard [28]3 years ago
8 0

Answer:

The molar mass of the unknown solute is 106,9 g/m

Explanation:

Cryoscopic descent formula to solve this

ΔT = Kf . m

Be careful because units in Kfp are K/m, so let's get the ΔT degrees °C in K

3,91°C  = 3,91 K

It's a difference, in the end it does not matter

For example you can have 5° C as the final temperature and as initial, 1,09 °C -- ΔT is 5 - 1.09 = 3.91

What happens in Kelvin?

5°C + 273 = 278 K

1,09° C + 273 = 274,09 K

ΔT = 278 K - 274,09 K = 3,91 K

3,91 K = 20,1 K/m * m

3,91 K / 20,1 m/K = m

0,194 = m (molality)

Molality means moles from solute in 1 kg of solvent.

1kg = 1000 g

1000 g ________  0,194 moles

50 g _________ x

x = (50 g * 13,77 moles) / 1000 g = 9,72 *10-3 moles

Moles = mass / molar mass

Molar mass = mass / moles

Molar mass = 1,04 g / 9,72 *10-3 moles

Molar mass = 106,9 g/m

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3 years ago
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Suppose 6.63g of zinc bromide is dissolved in 100.mL of a 0.60 M aqueous solution of potassium carbonate. Calculate the final mo
Alenkasestr [34]

Answer:

[Zn²⁺] = 4.78x10⁻¹⁰M

Explanation:

Based on the reaction:

ZnBr₂(aq) + K₂CO₃(aq) → ZnCO₃(s) + 2KBr(aq)

The zinc added produce the insoluble ZnCO₃ with Ksp = 1.46x10⁻¹⁰:

1.46x10⁻¹⁰ = [Zn²⁺] [CO₃²⁻]

We can find the moles of ZnBr₂ added = Moles of Zn²⁺ and moles of K₂CO₃ = Moles of CO₃²⁻ to find the moles of CO₃²⁻ that remains in solution, thus:

<em>Moles ZnB₂ (Molar mass: 225.2g/mol) = Moles Zn²⁺:</em>

6.63g ZnBr₂ * (1mol / 225.2g) = 0.02944moles Zn²⁺

<em>Moles K₂CO₃ = Moles CO₃²⁻:</em>

0.100L * (0.60mol/L) = 0.060 moles CO₃²⁻

Moles CO₃²⁻ in excess: 0.0600moles CO₃²⁻ - 0.02944moles =

0.03056moles CO₃²⁻ / 0.100L = 0.3056M = [CO₃²⁻]

Replacing in Ksp expression:

1.46x10⁻¹⁰ = [Zn²⁺] [0.3056M]

<h3>[Zn²⁺] = 4.78x10⁻¹⁰M</h3>

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3 years ago
What scientist developed the Bohr model
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Pls help!<br> the chemical that is responsible for stopping reaction is called the ____
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Answer:

reactant

Explanation:

I watched a chem video and this is what they called it.

8 0
3 years ago
C2H4+
klasskru [66]

Answer:

A. Theoretical yield = 3.51g

B. %yield = 75%

Explanation:

The balanced equation for the reaction is given below:

C2H4 + 3O2 —> 2CO2 + 2H2O

Molar Mass of O2 = 16 x 2 = 32g/mol

Mass of O2 from the balanced equation = 3 x 32 = 96

Molar Mass of H20 = (2x1) + 16 = 18g/mol

Mass of H2O from the balanced equation = 2 x 18 = 36g

A. From the equation,

96g of O2 produced 36g of H2O

Therefore, 9.35g of O2 will produce = (9.35 x 36)/96 = 3.51g of H2O

Therefore,theoretical yield of water (H2O) = 3.51g

B. Theoretical yield = 3.51

Actual yield = 2.63g

%yield =?

%yield = Actual yield/Theoretical yield x 100

%yield = 2.63/3.51

%yield = 75%

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3 years ago
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