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VLD [36.1K]
3 years ago
14

Water is a good choice of solvent because it is benign, cheap and readily available. Identify two characteristics that make wate

r a good choice for the recrystallization solvent for benzoic acid? (What are the characteristics of a good recrystallization solvent?)
Chemistry
2 answers:
mina [271]3 years ago
6 0

Explanation:

Characteristics of good solvent choice for the recrystallization.

1. Water has low solubility of benzoic acid at room temperature.

2. Cold water's low solubility of  benzoic acid allows for the high concentration production of crystal. And these crystals could be easily soluble in hot water.

3. Water dissolves soluble impurities well at  the room temperature.

Contact [7]3 years ago
3 0

Explanation:

It is known that a compound is soluble when the boiling point of the solvent is high. Whereas at normal temperature of the solvent it will have low solubility.

And, if the solute is highly soluble into the solvent at normal temperature then it is difficult to recrystallize the solute.

Hence, in order to recrystallize the solute particles it is necessary that impurities will be highly soluble at the room temperature or they should remain insoluble into the hot solvent.

As a result, there will not take place any reaction between the solute and solvent.

Since, benzoic acid is non-polar in nature and water is a polar solvent so, it will not easily dissolve in water. Therefore, it will readily evaporate in order to give the pure compound.

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Calculate the molality for each of the following solutions. Then, calculate the freezing-point depression ΔTF = iKFcm produced b
zlopas [31]

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

7 0
3 years ago
A gas made up of atoms escapes through a pinhole times as fast as gas. Write the chemical formula of the gas.
Artemon [7]

A gas made up of atoms escapes through a pinhole 0.225times as fast as gas. Write the chemical formula of the gas.

Answer:

Explanation:

To solve this problem, we must apply Graham's law of diffusion. This law states that "the rate of diffusion or effusion of a gas is inversely proportional to the square root of its molecular mass at constant temperature and pressure".

Mathematically;

                 \frac{r_{1} }{r_{2} }  = \frac{\sqrt{m_{2} } }{\sqrt{m_{1} } }

r₁ is the rate of diffusion of gas 1

r₂ is the rate of diffusion of gas 2

m₁ is the molar mass of gas 1

m₂ is the molar mass of gas 2

let gas 2 be the given H₂;

   molar mass of H₂ = 2 x 1 = 2gmol⁻¹

rate of diffusion is 0.225;

  i .e r1/r2 = 0.225

          0.225 = √2  /  √ m₁

           0.225 = 1.414 / √ m₁

           

       √ m₁  = 6.3

           m₁  = 6.3²  = 39.5g/mol

The gas is likely Argon since argon has similar molecular mass

5 0
3 years ago
Humans depend on water from various sources for different reasons. All of these sources are polluted or could be polluted to som
goldenfox [79]

Explanation:

Earth is known as the "Blue Planet" because 71 percent of the Earth's surface is covered with water. Water also exists below land surface and as water vapor in the air. Water is a finite source. The bottled water that is consumed today might possibly be the same water that once trickled down the back of a wooly mammoth. The Earth is a closed system, meaning that very little matter, including water, ever leaves or enters the atmosphere; the water that was here billions of years ago is still here now. But, the Earth cleans and replenishes the water supply through the hydrologic cycle.

please mark as brainliest

8 0
3 years ago
This earth system contains water and warms the atmosphere.
sleet_krkn [62]

Answer:

D

Explanation:

4 0
3 years ago
A sample of nitrogen gas expands in volume from 16 L to 5.4 L at constant
xxTIMURxx [149]

a. W = 0 J

b. W = - 308.028 J

<h3>Further explanation</h3>

Given

Nitrogen gas expands in volume from 1.6 L to 5.4 L

Required

The work done

Solution

Isothermal :

W = -P . ΔV

Input the value :

a. At a vacuum, P = 0

So W = 0

b. At pressure = 0.8 atm

W = - 0.8 x ( 5.4 - 1.6)

W = -3.04 L.atm ( 1 L.atm = 101.325 J)

W = - 3.04 x 101.325

W = - 308.028 J

6 0
3 years ago
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