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pychu [463]
3 years ago
6

From the list of the instructions and tips below, select the statement that would NOT lead to a successful recrystallization O D

ry the crystals by pulling air through after vacuum filtration (to help them dry). O Keep the crystals open to the air for quite a while during the drying step. O Precipitate the crystals as fast as possible. O Rinse the crystals on the filter with a small amount of the ice-cold solvent. O Use a very small amount of ice-cold solvent and a spatula to remove any crystals left in the flas
Chemistry
1 answer:
Pachacha [2.7K]3 years ago
5 0

Answer:

C. Precipitate the crystals as fast as possible

Explanation:

C. Precipitate the crystals as fast as possible

Precipitation if done fast , can lead to the formation of impure crystals , as impurities also get stuck inside the crystals. So it must be done slowly to obtain the pure crystals . Slower the crystals form , purer they are .

All the other options can lead to a successful recrystallization.  

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There are two steps in the usual industrial preparation of acrylic acid, the immediate precursor of several useful plastics. In
Scorpion4ik [409]

Answer:

The net change in enthalpy for the formation of one mole of acrylic acid from calcium carbide, water and carbon dioxide is -470.4 kJ/mol.

Explanation:

Step 1 : Calcium carbide and water react to form acetylene and calcium hydroxide

CaC_2(s)+2H_2O(g)\rightarrow

             C_2H_2(g)+Ca(OH)_2(s),\Delta H_1=-414 kJ..[1]

Step 2 : Acetylene, carbon dioxide and water react to form acrylic acid

6C_2H_2(g)+3CO_2(g)+4H_2O(g)\rightarrow 5CH_2CHCOOH(g),\Delta H_2=132 kJ..[2]

Using Hess's law:

[1] × 6 + [2]

6CaC_2(s)+16H_2O(g)+3CO_2\rightarrow 5CH_2CHCOOH(g)+6Ca(OH)_2(s),\Delta H_3=?

\Delta H_3=6\times \Delta H_1+\Delta H_2

\Delta H_3=6\times (-414 kJ)+132 kJ=-2352 kJ

The energy released on formation of 5 moles of acrylic acid = -2352 kJ

The energy released on formation of 1 moles of acrylic acid :

=\frac{-2352 kJ}{5 mol}=-470.4 kJ/mol

Hence, the net change in enthalpy for the formation of one mole of acrylic acid from calcium carbide, water and carbon dioxide is -470.4 kJ/mol.

5 0
2 years ago
What are the products of the balanced equation for the combustion of C8H17OH ?
erastova [34]
C8H17OH + 12O2 —> 8CO2 + 9H2O
3 0
3 years ago
Describe 2 ways of salting out proteins ​
liubo4ka [24]

The phenomenon known as "salting-out" occurs at very high ionic strengths, when protein solubility declines as ionic strength rises. As a result, salting out may be used to segregate proteins according to how soluble they are in salt solutions.

Because large levels of sodium chloride disturb the bonds and structure of the active site, the rate of enzyme activity will gradually decrease as the concentration of sodium chloride rises. As a result, some of the active sites get denaturized and the starch loses its ability to attach to them. As more enzymes get denatured and eventually cease to function, enzyme activity will steadily wane.

8 0
2 years ago
1. Calculate the average reaction rate expressed in moles H2 consumed per liter per second.
valentina_108 [34]

Answer:

1) 0.0025 mol/L.s.

2) 0.0025 mol/L.s.

Explanation:

  • For the reaction:

<em>H₂ + Cl₂ → 2HCl.</em>

<em></em>

<em>The average reaction rate = - Δ[H₂]/Δt = - Δ[Cl₂]/Δt = 1/2 Δ[HCl]/Δt</em>

<em></em>

<em>1. Calculate the average reaction rate expressed in moles H₂ consumed per liter per second.</em>

<em></em>

The average reaction rate expressed in moles H₂ consumed per liter per second = - Δ[H₂]/Δt = - (0.02 M - 0.03 M)/(4.0 s) = 0.0025 mol/L.s.

<em>2. Calculate the average reaction rate expressed in moles CI₂ consumed per liter per second.</em>

<em></em>

The average reaction rate expressed in moles Cl₂ consumed per liter per second = - Δ[Cl₂]/Δt = - (0.04 M - 0.05 M)/(4.0 s) = 0.0025 mol/L.s.

7 0
3 years ago
If the initial volume is 55ml and the final volume after some rocks of sandstone are added is 65ml what is the volume of the chi
AfilCa [17]

Answer:

Volume = 10ml

Density = 1/5 g/ml or 0.20g/ml

Explanation:

The rocks are 10ml since the initial volume went up by 10.

Since density = mass/volume, you divide 2 by 10.

D = 2/10

D = 1/5 g/ml or 0.20g/ml

(Unit is g/ml aka grams/millileter)

7 0
2 years ago
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