Question 4 of 10

For each process, predict the sign on the entropy change and write a sentence or two to explain how to make this prediction with

MrRa [10]

Answer: a. A solid melts: $\Delta S=+ve$

b. a vapor is converted to solid: $\Delta S=-ve$

c. a liquid freezes: $\Delta S=-ve$

d. A solid sublimes: $\Delta S=+ve$

e. a vapor condenses to liquid : $\Delta S=-ve$

f. a liquid boils: $\Delta S=+ve$

g. dissolving a tablespoon of salt in water: $\Delta S=+ve$

h. combustion of gasoline: $\Delta S=+ve$

Explanation:

Entropy is the measure of randomness or disorder of a system. If a system moves from an ordered arrangement to a disordered arrangement, the entropy change is negative and vice versa.

a. A solid melts: The solid is converting to liquid, thus the randomness is increasing as the molecules are moving away and the intermolecular forces are getting weaker. Thus the entropy change $(\Delta S)$ is positive.

b. a vapor is converted to solid: The gas is converting to solid, thus the randomness is decreasing as the molecules are moving close and the intermolecular forces are getting stronger Thus the entropy change $(\Delta S)$ is negative.

c. a liquid freezes: The liquid is converting to solid, thus the randomness is decreasing as the molecules are moving close and the intermolecular forces are getting stronger. Thus the entropy change $(\Delta S)$ is negative.

d. A solid sublimes: The solid is converting to gas, thus the randomness is increasing as the molecules are moving away and the intermolecular forces are getting weaker. Thus the entropy change $(\Delta S)$ is positive.

e. a vapor condenses to liquid : The gas is converting to liquid, thus the randomness is decreasing as the molecules are moving close and the intermolecular forces are getting stronger. Thus the entropy change $(\Delta S)$ is negative.

f. a liquid boils: The liquid is converting to gas, thus the randomness is increasing as the molecules are moving away and the intermolecular forces are getting weaker. Thus the entropy change $(\Delta S)$ is positive.

g. dissolving a tablespoon of salt in water: The solid is converting to ions , thus the randomness is increasing as the ions can move freely. Thus the entropy change $(\Delta S)$ is positive.

h. combustion of gasoline: The liquid is converting to gas, thus the randomness is increasing as the molecules are moving away and the intermolecular forces are getting weaker. Thus the entropy change $(\Delta S)$ is positive.

6 0

2 years ago

Calculate the mass, in grams, of cucl2 (mw = 134.452 g/mol) required to prepare 250.0 ml of a 6.11 % w/v cu2 (mw = 63.546 g/mol)

Sever21 [200]

6.11% w/v of Cu2+ implies that 6.11 g of Cu2+ is present in 100 ml of the solution

therefore, 250 ml of the solution would have: 250 ml * 6.11 g/100 ml = 15.275 g

# moles of Cu2+ = 15.275 g/63.546 g mole-1 = 0.2404 moles

1 mole of CuCl2 contain 1 mole of Cu2+ ion

Hence, 0.2404 moles of Cu2+ would correspond to 0.2404 moles of CuCl2

Molar mass of CuCl2 = 134.452 g/mole

The mass of CuCl2 required = 0.2404 moles * 134.452 g/mole = 32.32 grams

6 0

2 years ago

Can some one plz help

blsea [12.9K]

The reaction uses B) 9.0 g Br₂.

iron + bromine ⟶ product

2.0 g + x g ⟶ 11.0 g

According to the Law of Conservation of Mass, the total mass of the reactants must equal the total mass of the products.

∴2.0 + x = 11.0

x = 11.0 – 2.0 = 9.0

The reaction uses 9.0 g Br₂.

5 0

2 years ago

A gas sample occupies a volume of 1.264 L when the temperature is 168.0 °C and the pressure is 946.6 torr. How many molecules ar

alukav5142 [94]

Answer:

0.26×10²³ molecules

Explanation:

Given data:

Volume of gas = 1.264 L

Temperature = 168°C

Pressure = 946.6 torr

Number of molecules of gas = ?

Solution:

Temperature = 168°C (168+273= 441 K)

Pressure = 946.6 torr (946.6/760 = 1.25 atm)

Now we will determine the number of moles.

PV = nRT

P= Pressure

V = volume

n = number of moles

R = general gas constant = 0.0821 atm.L/ mol.K

T = temperature in kelvin

n = PV/RT

n = 1.25 atm ×1.264 L / 0.0821 atm.L/ mol.K ×441 K

n = 1.58 /36.21 /mol

n = 0.044 mol

Now we will calculate the number of molecules by using Avogadro number.

1 mol = 6.022×10²³ molecules

0.044 mol × 6.022×10²³ molecules/ 1mol

0.26×10²³ molecules

5 0

2 years ago

List 3 categories of properties used to classify solids.

NNADVOKAT [17]

Answer : Broadly solids are divided into three categories;

i) Crystalline solids have a regular definite structure, in which the particles pack in a repeating pattern from one edge of the solid to the other.

ii) Amorphous solids have a random structure, with little unorganized pattern long-range order.

iii) Polycrystalline solids are those where an aggregate which consists of a large number of small crystals or grains in which the structure is regular, but the crystals or grains are found to be arranged in a random fashion.

Also solids can be divided into 3 more categories according to their bonds;

i) Covalent solids, like diamond, which forms crystals that can be viewed as a single giant molecule made up of an almost endless number of covalent bonds.

ii) Ionic solids are basically salts, such as NaCl, in which the molecules are held together by the strong force of attraction between ions of opposite charge.

iii) Metallic solids are found in metals which have the force of attraction between atoms of metals, such as copper and aluminum, or alloys, such as brass and bronze, are metallic bonds.

8 0

2 years ago

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