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Topic: a combination of questions  (Read 9500 times)

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777888

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a combination of questions
« on: December 31, 2004, 02:22:12 PM »
I am studying for my exams. I found some concepts that are confusing me! Can somebody help me? I would appreciate! :)

Quantum
1. Why "matter and energy are not distinct...energy is a form of matter"?

Structure and properties of solids
2.What is a crystal lattice?

3. (i) and (ii) are from my text book, they seem to contradict each other. I don't know which INTERMOLECULAR force is stronger...ionic or network covalent?
Quotes:
Ionic crystals:
(i)"In general, ionic bonding is much stronger than all intermolecular forces"
Covalent network crystals:
(ii)"the overall bonding in the large marcromolecule of a covalent network is very strong -- stronger than most ionic bonding and intermolecular bonding"

4.Is it true that ionic compounds generally have high solubility in water, and molecular compounds generally have low solubility in water?

Thank you :D
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purelion

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Re:a combination of questions
« Reply #1 on: January 01, 2005, 12:04:34 AM »
Quote from: 777888 on December 31, 2004, 02:22:12 PM
I am studying for my exams. I found some concepts that are confusing me! Can somebody help me? I would appreciate! :)

Quantum
1. Why "matter and energy are not distinct...energy is a form of matter"?

Structure and properties of solids
2.What is a crystal lattice?

3. (i) and (ii) are from my text book, they seem to contradict each other. I don't know which INTERMOLECULAR force is stronger...ionic or network covalent?
Quotes:
Ionic crystals:
(i)"In general, ionic bonding is much stronger than all intermolecular forces"
Covalent network crystals:
(ii)"the overall bonding in the large marcromolecule of a covalent network is very strong -- stronger than most ionic bonding and intermolecular bonding"

4.Is it true that ionic compounds generally have high solubility in water, and molecular compounds generally have low solubility in water?

Thank you :D
4.Is it true that ionic compounds generally have high solubility in water, and molecular compounds generally have low solubility in water?
it is true.because the water is ...

1. Why "matter and energy are not distinct...energy is a form of matter"?

maybe.i am not sure.i think it is.
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Offline Donaldson Tan

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Re:a combination of questions
« Reply #2 on: January 01, 2005, 12:42:47 AM »
Happy New Year!!!

1. E = mc2 relates the amount of mass to its equivalent in terms of energy. E refers to energy, m refers to the mass of interest and c refers to the speed of light.

2. crystal lattice refers to regular pattern of atoms, ions, molecules in a crystalline substance. a crystal lattice can be regarded as a repeated translation of a unit cell of the lattice.

3i. there is no intermolecular forces in ionic crystals. ionic crystals consist of opposite charged ions. each ion are held in place by a balance of electrostatic attraction and repulsion. melting an ionic crystal would therefore involves overcoming the ionic bond between each ions to form molten state.

3ii. intermolecular force isn't a covalent bond. a covalent bond is formed when an electron pair is shared between 2 nuclei.

4. it is true because ionic compound consist of ions. each ion is capable of attracting the opposite charged dipole of the water molecule. the energy evolved from the ion-dipole bond is called hydration energy. usually, the hydration energy is sufficient to overcome the ionic bonds, thus an ionic compound is usually water-soluble. covalent compound usually dont contain significant dipoles that is capable of attracting water molecules. Hence, covalent compound are usually water-insoluble
« Last Edit: January 01, 2005, 12:44:06 AM by geodome »
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Jopster7

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Re:a combination of questions
« Reply #3 on: January 02, 2005, 08:08:33 AM »
just wanted to add, covalent bonds are stronger than ionic bonds and both are stronger than intermolecular bonds.
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777888

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Re:a combination of questions
« Reply #4 on: January 02, 2005, 10:53:51 AM »
Happy new year! :)

"...covalent bonds are stronger than ionic bonds "
WHY?
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Offline Mitch

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Re:a combination of questions
« Reply #5 on: January 02, 2005, 06:28:58 PM »
Quote from: Jopster7 on January 02, 2005, 08:08:33 AM
just wanted to add, covalent bonds are stronger than ionic bonds and both are stronger than intermolecular bonds.

That's not a true statement by any means. Firstly what do you mean by stronger? Stronger by homolytic bond clevage or heterolytic clevage?
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777888

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Re:a combination of questions
« Reply #6 on: January 03, 2005, 10:20:41 AM »
Are network covalent bonding stronger than ionic bonding? (covalent network crystals have a higher melting point than ionic crrystals...)
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Demotivator

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Re:a combination of questions
« Reply #7 on: January 03, 2005, 10:40:57 AM »
I suppose network covalent bonds are stronger generally. Diamond is the ultimate example.
I think covalent bonds are of comparable strength to ionic bonds in general. Part of the difficulty is that most bonds are a mixture of character.
 There are cases where one type is stronger than the other. It depends on the specific material and the specific measurement for determining or defining "strength".
« Last Edit: January 03, 2005, 10:58:30 AM by Demotivator »
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777888

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Re:a combination of questions
« Reply #8 on: January 03, 2005, 05:03:06 PM »
oic...so network covalent bonds and ionic bonds are both intramolecular forces?
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Offline Mitch

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Re:a combination of questions
« Reply #9 on: January 03, 2005, 06:45:56 PM »
no, but they might have intermolecular forces. Lol, is that confusing enough?
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