How can we predict melting points?

Answers

Answer 1

Explanation:

Many of the properties of organic molecules can be predicted based on the strength of their cohesive molecule-molecule interactions (i.e. how much the molecules want to stick together).  The boiling point (BP) and melting point (MP) of an organic molecule is related to: 1) the molecular weight of the molecule and 2) the "stickiness" of individual molecules for their neighbors.  

   For example, molecules in a liquid are held together by attractive interactions between molecules.  These interactions must be broken (by adding heat) in order to transition into the gas.  The stronger the cohesive interactions, the more heat that is necessary for the liquid-to-gas phase transition.  These same attractive molecule-molecule interactions have to be broken for a solid to liquid phase change.

Examples: (Rank the following molecules in terms of MP and BP.)

 

Introduction to intermolecular forces:

All of the attractive intermolecular forces are based on the electrostatic attraction of positive charges on one molecule with negative changes.  The stronger the charges, the stronger the attraction between molecules.

How to:

In general, comparisons can only be made between molecules with similar formulas or molecular weights.*  First, identify the functional groups in the molecules being compared.  Each functional group can form different types of intermolecular interactions (see the chart above).  Interactions higher up on the chart form stronger cohesive interactions and will have higher boiling points and melting points.

* Note that larger molecules usually have higher boiling points and melting points.  This is not because of their higher molecular weights but because they usually have greater surface areas with which to form more intermolecular interactions.  This is also why linear molecules tend to have higher MPs and BPs than branched (or more spherically shaped) molecules.  Linear molecules will have more surface area than a more spherically shaped molecule.

All three molecules have approximately the same molecular formula and molecular weights.  Only molecule A contains a strongly polarized or ionic functional group: an aldehyde.  The C=O group in aldehydes generate a strong molecular dipole (partial + and - charges).  Thus, it can form weak attractive dipole-dipole interactions, and A will have the highest boiling point and highest melting point in this series of compounds.

Molecules B and C are alkanes.  They can only form the weakest attractive dispersion interactions between their molecular surfaces.  Due to its long-thin shape, B will have a greater surface area and can form more dispersion interactions than the rounder C.  Therefore, B will have a higher boiling point and melting point than C.

Molecule A is ionic (it has charges).  Therefore, it can form the strongest ion-ion interactions and will have the highest boiling point and melting point.

Molecule B is a carboxylic acid with an acidic proton and basic lone pairs.  Therefore, it can form medium strength hydrogen bonding interactions, and it will have the next highest boiling point and melting point.

Molecule C is a carboxylic ester, which is a polar functional group.  However, it does not have an acidic proton.  Therefore, esters cannot form hydrogen bonds with themselves.  Instead, they can only form weak dipole-dipole interactions and will have the lowest boiling point and melting point in this series of compounds.

Answer 2

Answer:

Explanation:

By thinking about non covalent intermolecular interactions, we can also predict relative melting points. All of the same principles apply: stronger intermolecular interactions result in a higher melting point.


Related Questions

please show the work :(What is the estimated force applied to the box if the acceleration is .40 m/s2?

force (N) acceleration (m/s2)
10 .20

? .40​

Answers

Answer:

20N

Explanation:

Given parameters:

        Force(N)     Acceleration(m/s²)  

            10                   0.2

           ?                      0.4

Unknown:

The force applied when the acceleration is 0.4m/s²

Solution:

From newton's second law of motion;

 Force = mass x acceleration

 Since we are using the same box, let us find the mass of the box;

      Force  = mass x acceleration

         10 = mass x 0.2

            mass = [tex]\frac{10}{0.2}[/tex]  = 50kg

Now,

 The force in the second instance will be;

      Force  = 50 x 0.4  = 20N

True or False: Neutrons have both a positive and negative charge

Answers

Answer:

false

Explanation:

Answer:

false

Explanation:

Ayala is making salad dressing. She mixes oil and
vinegar in a blender until a smooth consistency is
formed. Explain whether this is a heterogeneous or a
homogeneous mixture and why.

Answers

Answer:

A heterogeneous mixture

Explanation:

A heterogeneous mixture is a mixture that is not uniform in composition. This means that we can tell that there is more than one component in the mixture. An example of a heterogeneous mixture would be milk and cereal.

The opposite is a homogeneous mixture, which is uniform in composition. An example of a homogeneous mixture is air. There are many different particles surrounding us, but we can't tell.

A salad dressing that consists of oil and vinegar is another example of a heterogeneous mixture. Its consistency is smooth, but oil and vinegar can't dissolve each other, which means that we will see droplets of oil and vinegar. Since we can tell that it contains these components, this is a heterogeneous mixture.

Answer:

Sample Response: A homogeneous mixture can only form when one of the substances can dissolve the other one. Oil and water cannot dissolve each other, so they must form a heterogeneous mixture with small particles of vinegar dispersed throughout the oil, yet not dissolved.


Which gas is made from more than one element?

Answers

water, carbon, dioxide and methane

What Most Often Causes The Availability Of Water To Change?
A. type of plants
B. type of soil
C. local geography

Answers

Answer:the answer is C

Explanation:

A 2.9 kg model rocket accelerates at 15.3 m/s2 with a force of 44 N. Before launch, the model rocket was not moving. After the solid rocket engine ignited, hot gases were pushed out from the rocket engine nozzle and propelled the rocket toward the sky.

Which of Newton’s laws apply in this example? Check all that apply.

Answers

Answer:

newton's firts law

Explanation:

because it states that everybody continue its state in rest unless an external force is appy to change its state from rest to motion.

Answer:

A, B, C

Explanation:

Why do atoms form bonds with other atoms?
SELECT ALL THAT APPLY
a
To ensure that both atoms in the bond have eight total
electrons.
b To obey the octet rule.
С
To fill the outer electron shells of both atoms.
d
To achieve a more stable electron configuration for both
atoms.

Answers

c i believe if not i am sorry

The smallest unit that combines chemically or physically to form molecules and compounds is called an atom. They are composed of electrons and protons and neutrons in the nucleus.

The correct answer is:

Option d. To achieve a more stable electron configuration for both atoms.

This can be explained as:

Atoms do not always bond to complete eight electrons in their shells.

Atoms do not react to follow the octet rule.

Electrons don't need to be filled in the shells of atoms of both the shells as some atoms lose electrons too.

Therefore to achieve stable configuration atoms bond with other atoms.

To learn more about atoms and stability follow the link:

https://brainly.com/question/7615695

how to write the ionic formula for the K1+, MnO41- pair of ions

Answers

Answer:

Ionic formula: KMnO4

Explanation:

Pottasium permanganate (KMnO4) is an ionic compound that contains a combination of pottasium cations (K+) and permanganate anion (MnO4-). The pair of ions that make up the ionic compound cancel out each other to make it neutral.

K+ (aq) + MnO4- (aq) → KMnO4 (aq)

MnO4- contains 1 atom of manganese with a (+7) charge and four atoms of oxygen with a (-2) charge each. This forms a +7 for Mn and -8 for O4, hence, a net total of -1.

PLEASE HELP!!!!!! SpongeBob Scientific Method Practice

Mr. Krabbs wants to make Bikini Bottoms a nicer place to live. He has created a

new sauce that he thinks will reduce the amount of bodily gas that comes out after

eating krabby patties from the Krusty Krab. He brings in 100 customers that

always have gas problems. He has 50 of them (Group A) eat krabby patties with

the new "Gas-free" sauce. The other 50 (Group B) eat krabby patties with sauce

that looks just like the Gas-free sauce but is really the old sauce with food

coloring. Both groups were told that they were getting Gas-free sauce. Two

hours after eating the krabby patties, 30 customers in Group A reported having fewer

gas problems and 2 customers in Group B reported having fewer gas problems.

I

1. What is Krusty Krab's hypothesis? Krusty Krab's hypothesis is that he thinks his

new sauce will reduce the amount of bodily gas that comes out after eatin

Answers

Answer:

The hypothesis is that the new sauce used in hamburgers will be able to reduce the incidence of body gases in customers.

Explanation:

A hypothesis is an assumption about a specific topic that is being researched. In the case shown in the question above, Krusty Krab believes that the new sauce he wants to use in hamburgers is capable of reducing the amount of body gases created by the body. Krusty Krab wanted to do scientific research where he analyzed the efficiency of this new sauce, but he assumes that the new sauce is efficient in reducing the creation of these gases. This is a hypothesis.

List the following particles in size order, from biggest to smallest?
A Molecules, electrons, atoms incorrect answer
B Atoms, molecules, electrons incorrect answer
C Electrons, atoms, molecules incorrect answer
D Molecules, atoms, electrons

Answers

Answer:

D. Molecules, atoms, electrons.

Explanation:

I did a quiz on this and got it right

Answer:

D. Molecules, atoms, electrons.

Explanation:

i did the test trust i got it right

help me out plz!!!!​

Answers

I don’t see a problem anywhere

which of the following lists show the elements in order, from those having the least protons to those having the most protons in the atoms?

A. K, Mg, N, O
B. C, Al, P, Cl
C. Li, Be, H, He
D. Na, Ne, He, H​

Answers

Answer is b, trust. :)

The elements that have least protons to those having the most protons in the atoms are:

B. C, Al, P, Cl

Protons in an atom:

There is an equal number of protons and electrons in an atom. So when moving across a period in a periodic table the number of electrons increases which also shows the increases in a number of protons. So as the atomic number increases, the number of protons and electrons also increases.

Thus, the order of elements having least to greatest protons are:

C, Al, P, Cl

C has 6 atomic number, Aluminium has 13 atomic number , Phosphorus has 14 atomic number and atomic number of chlorine is 17.

Thus, option B is correct.

Find more information about Atomic number here:

brainly.com/question/1805828

The chemical equation represents a reaction between ammonia and oxygen to form nitrogen monoxide and water. 4 N H 3 ( g ) + 5 O 2 ( g ) → 4 NO ( g ) + 6 H 2 O ( g ) What is the limiting reagent when a 4.50 g sample of ammonia is mixed with 15.80 g of oxygen?

Answers

The limiting reagent : NH₃

Further explanation

A method that can be used to find limiting reactants is to divide the number of moles of known substances by their respective coefficients, and small or exhausted reactants become a limiting reactant

Reaction

4NH₃(g)+5O₂(g)⇒4NO(g)+6H₂O(g)

mol NH₃ :

[tex]\tt \dfrac{4.5}{17}=0.265[/tex]

mol O₂ :

[tex]\tt \dfrac{15.8}{32}=0.494[/tex]

mol ratio

NH₃ :

[tex]\tt \dfrac{0.265}{4}=0.06625[/tex]

O₂ :

[tex]\tt \dfrac{0.494}{5}=0.0988[/tex]

Limiting reactants : NH₃ (smaller ratio)

The limiting reagent when a 4.50 g sample of ammonia is mixed with 15.80 g of oxygen is NH₃

Calculation of limiting reagent:

The limiting reactant refers to the reactant that gets consumed first in a chemical reaction and thus it limits how much product can be created or developed. A method that can be used to determine limiting reactants that to divide the number of moles by their respective coefficients.

So,

For mol NH₃ :

[tex]= 4.5\div 17[/tex]

= 0.494

For mol O₂ :

[tex]= 15.8 \div 32[/tex]

= 0.494

For mol ratio

NH₃ :

[tex]= 0.265 \div 4[/tex]

= 0.06625

O₂ :

[tex]= 0.494 \div 5[/tex]

= 0.0988

Based on the above calculations we can say that it is NH₃

learn more about the oxygen here: https://brainly.com/question/19803828

When is the potential energy transformed into kinetic energy?

Answers

When it is in motion, i.e no longer stopped

Explanation:

If a ball is lifted to a certain height, it gains potential energy. If it is then dropped, the potential energy is converted into kinetic energy as it looses height but gains speed.

It is transformed when it is moving

Microwave warming Popcorn is a  example of

A. Conduction
B. Convection
C. Radiation
D. None of these

Answers

Answer:

A

Explanation:

Ttu67j5ri76tio5777t65y75ircyjutfjgtfv

Here is a model of the sun earth system at a certain point in earths orbit around the sun based on the model which statement best explains my point is is experiencing summer

Answers

Answer:

the earth is tilted towards the sun

Explanation:

In the context, there is a sun and earth system and at a certain point when the earth is moving in its orbit around he sun, some point on the earth experiences the summers season. This is because at this point of the earths revolution, the point on the earth is facing the sun and is also tilted towards the sun. So at this point the sun rays fall directly at the surface. While the place which is tilted away from the sun, experiences winter season.

Answer:

Earth's northern hemisphere is tilted toward the Sun.

What is the best explanation of an organelle?

Answers

An organelle is a structure within the cytoplasm of a eukaryotic cell that is enclosed within a membrane and performs a specific job. Although ribosomes are not enclosed within a membrane, they are still commonly referred to as organelles in eukaryotic cells.

Answer: A organelle is a structure within the cytoplasm of a eukaryotic cell that is enclosed within a membrane and performs a specific job and although ribosomes are not enclosed within a membrane, they are still commonly referred to as organelles in eukaryotic cells.

Find the density of a 720.0 g block of Titanium with these dimensions: L = 10.0 cm, W = 8.0 cm, H = 2.0 cm

Answers


D=m/V=0.72/0.1x0.08x0.02=4500(kg/m3)

Which property do metalloids share with nonmetals?

Answers

Answer:

Both can react to form acidic compunds. Both are brittle.

Explanation:

I need someones help

Answers

Answer:

y or z one of those two i think its z but im so sorry if im wrong if not z then try y also I learned this last year.

El plomo y el yodo forman dos compuestos. En uno, el porcentaje de en masa de plomo es del 44,94% y en el otro es de 62,02%. Calcula los gramos de plomo por gramos de yodo en cada compuesto

Answers

Answer:

0.8162 gramos de plomo por gramo de yodo

1.633 gramos de plomo por gramo de yodo

Explanation:

Asumiendo una base de 100 gramos para cada compuesto:

Primer compuesto:

Gramos plomo: 44.94g

Gramos de yodo: 100-44.94g = 55.06g

Así, la masa de plomo por gramos de yodo para el primer compuesto es:

44.94g plomo / 55.06g Yodo =

0.8162 gramos de plomo por gramo de yodo

Segundo compuesto:

Gramos plomo: 62.02g

Gramos de yodo: 100-62.02g = 37.98g

La masa de plomo por gramos de yodo para el segundo compuesto es:

62.02g plomo / 37.98g Yodo =

1.633 gramos de plomo por gramo de yodo

What mass of NO2 can be produced when 678 mL of oxygen at STP and 256 grams of NH3 are mixed together?

Answers

Answer:

WHT55

Explanation:

i experianced this before

HELP!!!!!! WILL MARK BRAINLIEST!!!


Fill in the blank.

Atoms are held together in molecules by _______.
_______ are compounds with the same chemical formula but different molecular structures.
A/An _______ indicates the ratio of atoms in a molecule.
_______ are similar to molecular formulas but show how atoms are bonded together.
When two atoms of the same element combine to form a molecule, this is called a _______ molecule.
The breaking and forming of bonds between atoms in substances results in changes in the _______ contained in the substances.
Respond to the following based on your reading.

Give two purposes for the systematic naming of chemicals.
Name the elements in the molecule H2SO4 and tell how many atoms of each element are present.
How many molecules are represented by 3CO2?

Answers

Answer:

1. Covalent Bond

2. Isomers

3. Molecular and Empirical Formula

4. The Structural Formula

5. Diatomic Molecules

1. Hydrogen and Tetraoxosulphate. There are 2 atoms of hydrogen and 4 atoms of tetraoxosulphate.

Explanation:

Sorry, I wrote all I know

Select all that apply. Choose the chemical formulas that are matched with their
correct name.


MgF2, magnesium (II) fluoride

BeO, beryllium oxide

NaCl, sodium chloride

AlF3, aluminum trifluoride

CaCl2, calcium chloride

Answers

Answer:

i think just these

NaCl

CaCl2

Identity the solution among the following mixture-air​

Answers

Answer:

Air is composed of about 78% nitrogen, 21% oxygen, and 1% of other gasses like carbon dioxide

Explanation:

Brainly deleted my answer so I came back to answer this again :(

I need help with the bottom part of the paper

Answers

Answer:

ur really pretty :)

Explanation:

The independent variable is the variable that you measure.
True or False?

Answers

Answer:

Maybe false

Explanation:

.........

when a substance melts the kinetic energy

A Decreases then increase

B Decrease

C Stays the same

D Increase

Answers

Answer:

C stays The same.

Is the answer.

Answer = C

the overall kinetic energy level between the two substances actually remains the same

An atom of an element has 2 electrons in the 1st energy level and 5 on the 2nd energy level what element is it ?

Answers

the element is nitrogen

5+2=7

Mrs. Moran and Mr. Moran decided to move the cabinet in their dining room. Mrs.
Moran stood on one side, and Mr. Moran stood on the other. They each pushed
with 30 N of force. What was the net force on the cabinet?

Answers

Answer:

60N

Explanation:

The net force on the cabinet is 60N.

 Net force is that single force that will act like all other forces on a body. The direction of the force and magnitude is very important when resolving forces.

  Force applied by Mrs. Moran  = 30N

  Force applied by Mr. Moran = 30N

                Since they each stood on both sides and pushed, the net force will be 30N + 30N  = 60N

Answer: 0

Explanation: If they both pushed a force of 30N then it doesn’t add up but instead you subtract. so it’s 0. ur yw ;)

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