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svp [43]
2 years ago
7

What is the freezing point of a solution of 498mL of water (solute) dissolved in 2.50 L of ethanol (solvent), C2H5OH? The densit

y of C2H5OH is 0.789g/cm3. (Remember that water has a density of 1.0 g/cm3.)
Chemistry
1 answer:
jok3333 [9.3K]2 years ago
7 0

Answer:

Freezing T° of solution is -142.4°C

Explanation:

This excersise is about colligative properties, in this case freezing point depression,

ΔT = Kf . m . i

Where ΔT = Freezing T° of solvent - Freezing T° of solution

Kf = Cryoscopic constant

m = mol/kg (molality)

i = Number of ions dissolved.

Water is not ionic, so i = 1

Let's find out m.

We determine mass of water, by density

498ml . 1 g/mL = 498 g

We convert the mass of water to moles → 498 g . 1mol/18g = 27.6 moles

We determine mass of solvent by density

2500 mL . 0.789 g/mL = 1972.5 g

Notice, we had to convert L to mL to cancel units.

1 cm³ = 1 mL

We convert the mass from g to kg → 1972.5 g . 1kg /1000g = 1.97kg

We determine m = mol/kg → 27.6mol / 1.97kg = 13.9 m

Kf for ethanol is: 1.99 °C/m

Freezing T° for ethanol is: -114.6°C

We replace at formula: - 114.6°C - Freezing T° solution = 1.99 °C/m . 13.9 m . 1

- 114.6°C - Freezing T° solution = 27.8 °C

- Freezing T° solution  = 27.8°C + 114.6°C

Freezing T° Solution = - 142.4 °C

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Explanation:

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6 0
2 years ago
If 15.0 mL of phosphoric acid completely neutralizes 38.5 mL of 0.150 mol/L calcium hydroxide, what is the concentration of the
Sedbober [7]

Answer:

Let me give it a try.

H3PO4 + Ca(OH)2 = Ca3(PO4)2 + H2O

Balancing this reaction

2H3PO4 + 3Ca(OH)2 == Ca3(PO4)2 + 6H2O.

Moles= Molarity x Volume

Volume = 38.5ml = 0.0385L

Moles of Ca hydroxide = 0.150m/L x 0.0385L

(Notice the units canceling out...leaving moles).

=0.005775moles of Ca(OH)2.

From balanced reaction...

3moles of Ca(OH)2 completely reacts with 2moles of H3PO4

0.005775moles of Ca(OH)2 would completely react with....

= 0.005775 x 2/(3)

=0.00385moles of H3PO4.

Now we're looking for its Concentration in Mol/L

Molarity=Moles of solute/Volume of solution(in L)

Volume of solution assuming no other additions to the reaction = 15ml + 38.5ml =53.5ml =0.0535L

Molarity = 0.00385/0.0535

=0.072Mol/L.

If this is wrong

then Simply Try The formula for Mixing of solutions

C1V1 = C2V2

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7 0
3 years ago
A balloon that had a volume of 3.50 L at 25.0°C is placed in a hot room at 40.0°C. If the pressure remains constant at 1.00 atm,
Ad libitum [116K]
The answer is 3.68 L
8 0
3 years ago
Read 2 more answers
a sample of unknown material weighs 500 n in air and 200 n when immesersed in alcholol with a specfic gravity of 0.7 what is the
svet-max [94.6K]

Answer: The mass density is 1166.36 kg/m^{3}.

Explanation:

Given: Weight of sample in air (F_{air}) = 500 N

Weight of sample in alcohol (F_{alc}) = 200 N

Specific gravity = 0.7 = 0.7 \times 1000 = 700 kg/m^{3}

Formula used to calculate Buoyant force is as follows.

F_{B} = F_{air} - F_{alc}\\= 500 - 200 \\= 300 N

Hence, volume of the material is calculated as follows.

V = \frac{F_{B}}{\rho \times g}

where,

F_{B} = Buoyant force

\rho = specific gravity

g = acceleration due to gravity = 9.81

Substitute the values into above formula.

V = \frac{F_{B}}{\rho \times g}\\= \frac{300}{700 \times 9.81}\\= \frac{300}{6867}\\= 0.0437 m^{3}

Now, mass of the material is calculated as follows.

mass = \frac{F_{air}}{g}\\= \frac{500 N}{9.81}\\= 50.97 kg

Therefore, density of the material or mass density is as follows.

Density = \frac{mass}{volume}\\= \frac{50.97 kg}{0.0437 m^{3}}\\= 1166.36 kg/m^{3}

Thus, we can conclude that the mass density is 1166.36 kg/m^{3}.

7 0
2 years ago
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To balance the reactions, number of electrons need to be balanced. 
Multiply 1st reaction by 3
Multiply 2nd reaction by 2
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add the 2 equations 
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add 6NO₃⁻ ions to each side 
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4 0
3 years ago
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