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sveticcg [70]
3 years ago
10

A) Calculate the osmotic pressure difference between seawater and fresh water. For simplicity, assume thatall the dissolved salt

s in seawater are NaCl.
b) Reverse osmosis occurs when you apply a pressure difference greater than the osmotic pressure to asolution separated from a pure solvent by a membrane permeable only to the solvent. In this process, thesolvent flows out of the solution and this can be used to desalinate sea water. Use your result from Part (a)to find the minimum work required to desalinate one liter of water.

c) It is also possible to desalinate water by evaporation. The water vapor is recondensed and the salt is leftbehind. Compare your result from part (b) with the amount of heat that would be required to evaporate aliter of water. Assume that the water starts at a temperature of 300K and the latent heat of vaporization at apressure of one atmosphere is 40.7kJ/mol. Compare your result with that of Part (b)
Chemistry
1 answer:
never [62]3 years ago
6 0

Answer:

a)  Δπ = 1.264 atm

b) W = 128 joules

c)  ΔH >> W  ( a factor greater than 17,000 )

Explanation:

a) The osmotic pressure, π , is determined by :

π = nRT/V, where n= moles of solute

                          R= 0.0821 Latm/kmol

                          T = 300 K

calling π(sw) osmotic pressure for  for sea water and π (fw) for fresh water,

salinity of sea water = 3.5 g / 1L water   (assuming only NaCl for the salts)

salinity of fresh water = 0.5 parts per thousand (range: 0- 0.5 ppt)

πsw = (3.5 g/58.44 g/mol) (0.0821 Latm/Kmol) (300 K ) /1 L = 1.475 atm

πfw = (0.5 g/58.44 g/mol) (0.0821 Latm/Kmol) (300 K ) /1 L = 0.211 atm

d water = 1 g/cm³

Δ π = (1.475 - 0.211) = 1.264 atm

b) W = Δπ V = 1.426 atm x 1L = 1.43 L-atm

1 L-atm = 101.33 j

W =  101.33 j/ Latm x  1.43 Latm = 128 joules

c) ΔH = Q₁ + nΔH vap, where

            Q₁  = heat required to bring the solution from 300 K to boiling, 373 K

            ΔH vap = heat of vaporization

Q = mCΔT = 1000 g x 4.186 j x 73 K = 305.6 j = 0.3056 kj

ΔH vap = (1000 g/ 18 g/mol ) 40.7 kj/mol = 2,261 kj

ΔH =  0.3056 kj + 2,261 kj = 2,261.3 kj

Note = Q << ΔH vap and we could have neglected it.

This result shows why nobody talks about evaporation of sea water to produce fresh water ΔH >> W

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Describe an experiment for the preparation and collection of Oxygen sodium peroxide​
vitfil [10]

Answer:

Making oxygen

Oxygen can be made from hydrogen peroxide, which decomposes slowly to form water and oxygen:

hydrogen peroxide → water + oxygen

2H2O2(aq) → 2H2O(l) + O2(g)

The rate of reaction can be increased using a catalyst, manganese(IV) oxide. When manganese(IV) oxide is added to hydrogen peroxide, bubbles of oxygen are given off.

Apparatus arranged to measure the volume of gas in a reaction. Reaction mixture is in a flask and gas travels out through a pipe in the top and down into a trough of water. It then bubbles up through a beehive shelf into an upturned glass jar filled with water. The gas collects at the top of the jar, forcing water out into the trough below.

To make oxygen in the laboratory, hydrogen peroxide is poured into a conical flask containing some manganese(IV) oxide. The gas produced is collected in an upside-down gas jar filled with water. As the oxygen collects in the top of the gas jar, it pushes the water out.

Instead of the gas jar and water bath, a gas syringe could be used to collect the oxygen.

5 0
3 years ago
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Levart [38]

Answer:

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Explanation:

7 0
3 years ago
1. What is the density of a 20 gram of 40 ml liquid?
____ [38]

Answer:

1. 0.5 g/mL

2. 0.88 g/cm^3

3. It has the greatest mass to volume ratio

4. Incomplete

5. H^+ (aq)+OH^-(aq)\rightleftharpoons H_2O (l)

6. 1

7. Gloves, goggles, coat, mask

8. Flush with tap water for at least 15 minutes

9. The facts are listed below

10. Mass and volume

12. All matter consists of moving particles, the degree of their movement is directly proportional to their kinetic energy

Explanation:

1. In order to solve for density, we should know that density is the ratio between mass and volume of a liquid. In this case, we're given both measures: given mass of m = 20 g and volume of V = 40 mL, we may simply apply the equation of density described here:

d=\frac{m}{V}

Substituting the variables, we obtain:

d=\frac{m}{V}=\frac{20 g}{40 mL}=0.5 g/mL

2. Given a mixture of several liquids, it's important to understand that liquids with a greater density will tend to form a bottom layer of a solution, while liquids with a lower density will tend to form a top layer of a solution. Here we have a liquid with a density of d_1 = 1.0 g/cm^3 and another liquid with a density of d_2 = 0.88 g/cm^3. Notice that d_1 > d_2.

This implies that the liquid with a density of 0.88 g/cm^3 would be on top, as its density is lower than the density of the other liquid with a density of 1.0 g/cm^3.

3. The solid phase is not always, but typically denser than liquids or gases. There are some exceptions to this rule, for example, ice, a solid phase of water, is less dense than liquid water.

However, for the majority of cases this statement is true. Remember that solid phases are the most ordered phases with atoms being packed closely to each other. In liquids, atoms are more dispersed with distances between them being greater than those in solids. Similarly, gases have the greatest distances between gas atoms among all three phases.

Since density is directly proportional to mass, let's say we take the same volume of a solid, a liquid and a gas. For the same volume, since we'll have a greater number of solid atoms than for a liquid or a gas (because solid atoms are more closely packed with lower average distances between the atoms), the mass to volume ratio will be the greatest for solids.

4. This seems to be an incomplete question.

5. In order to balance the following ionic equation, we need to follow the mass and charge balancing rules. Firstly, expand a water molecule showing the individual parts of it:

H-OH

Secondly, notice that we need to add a hydroxide anion to the proton, so that we obtain the same number of protons and hydroxide anions on the left side, as well as the number of hydrogen and oxygen atoms on the right. This way, the net charge on the left hand side (0) and the net charge on the right hand side (0) are equal, so the charge is balanced as well. We obtain:

H^+ (aq)+OH^-(aq)\rightleftharpoons H_2O (l)

6. We should be familiar with the ionization constant of water in the context of this problem. It is defined as the product between the hydronium ions and hydroxide ions and is a constant number at some given temperature. For pure water, the concentration of hydronium ions is balanced by the concentration of hydroxide anions to yield a neutral pH value, meaning the ratio of one with respect to the other would be 1.

For example, at room temperature, the ionization constant of water is defined as:

K_w=[H^+][OH^-]=10^{-14}

Since we have pure water:

[H^+]=[OH^-]=\sqrt{10^{-14}}=10^{-7}

Then the ratio is:

[tex]\frac{[H^+]}{[OH^-]}=\frac{10^{-7}}{10^{-7}}=1

7 to 12. The questions are explained in the file attached.

Download pdf
4 0
4 years ago
Suppose of lead(II) acetate is dissolved in of a aqueous solution of ammonium sulfate. Calculate the final molarity of acetate a
Lynna [10]

Answer:

0.294 M

Explanation:

The computation of the final molarity of acetate anion is shown below:-

Lead acetate = Pb(OAc)2

Lead acetate involves two acetate ion.

14.3 gm lead acetate = Mass ÷ Molar mass

= 14.3 g ÷ 325.29 g/mol

= 0.044 mole

Volume of solution = 300 ml.

then

Molarity of lead is

= 0.044 × 1,000 ÷ 300

= 0.147 M

Therefore the molarity of acetate anion is

= 2 × 0.147

= 0.294 M

3 0
4 years ago
Which properties can be measured without changing the chemical composition of the matter? _______ properties can be measured wit
evablogger [386]

Answer:

\boxed {\sf Physical}

Explanation:

There are two main kinds of properties: chemical and physical.

Chemical properties, like the name suggests, have to be observed by changing the chemical composition.

That leaves <u>physical properties.</u> They can be measured without any chemical composition changes.

Some examples include: color, odor, mass, density, and volume. All can be measured with just the senses or measuring tools and no composition alterations are needed.

3 0
3 years ago
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