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lidiya [134]
3 years ago
6

What are the Lewis definitions of an acid and a base? In what way are Bronsted definitions? they more general than the In terms

of orbitals and electron arrangements, what must be present for a molecule or an ion to act as a Lewis acid (use HT and BF3 as examples)? What must be present for a molecule or ion to act as a Lewis base (use OH and NH3 as examples)?
Chemistry
1 answer:
kati45 [8]3 years ago
4 0

Explanation:

Lewis definition of Acids and Bases

Chemical species which are capable of accepting electron pairs or donating protons are called Lewis acid.

Chemical species which are capable of donating electron pairs or accepting protons are called Lewis base.

Bronsted definition of acids and bases

Chemical species which are capable of donating H+ are called Bronsted acids.

Chemical species which are capable of accepting H+ are called Bronsted bases.

So all Bronsted acids are Lewis acids but all Lewis acids are not Bronsted acids.

For a chemical species to behave as Lewis acid, they must have:

  • Incomplete octet
  • Double bond
  • Vacant d-orbitals

For example, in BF3, octet of boron is incomplete, so it can accept a pair of electron and behaves as Lewis acid.

For a chemical species to behave as Lewis base, they must have:

  • lone pair of electrons

For example, NH3 and OH, both N and O have lone pairs of electrons, hence behave as Lewis base.

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Carbon dioxide is a gaseous molecule made up of the elements, C and O. Each mole of carbon dioxide has one mole C and two mole oxygen atoms.

Molar mass of carbon dioxide (CO_{2})=(1 * 12.01\frac{g}{mol}) +(2* 16\frac{g}{mol})=44.01\frac{g}{mol}

Percentage by mass of carbon = \frac{(1*12.01\frac{g}{mol}) }{44.01\frac{g}{mol} } *100=27.3%

Percentage by mass of oxygen = \frac{(2*16\frac{g}{mol})}{44.01\frac{g}{mol} } *100=72.7%

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12. Which compound can act as both a BrønstedLowry
oksian1 [2.3K]
1) The compound which can act as a <span>Bronsted-Lowry acid and a Bronsted-Lowry base is definitely water - H2O. Remember that water is </span><span>amphoteric which means it can </span>either accept protons or donate them, so it is the most proper option among other represented. Here are examples of both base and acid with water : <span>HCl+H20=H30+Cl ; </span><span>NH3+H2O=NH4+OH 

2) The </span><span>acids in this equilibrium reaction CN– + H2O HCN + OH. Acid species always donate </span> H+ to the species with which they react. In the second option you can see how H2O donates an H+ to CN-. If the reaction gets reversed we will obtain<span> HCN that donates an H+ to OH that shows that it is an acid.
</span><span>
3) </span>The products of self-ionization of water are OH⁻ and H₃O⁺. Self-ionization is an ionization reaction during which  H2O deprotonates its hydrogen atoms to become a hydroxide ion -- OH−. After this process OH-  protonates another water molecule forming H3O+<span>. 

4) The type of </span> solution which is one with a pH of 8 is acidic. Here is a little table that can be a prompt for you if you ever come across such tasks - ph : 7 is neutral<span>. </span>pH<span>  </span>lower than 7<span> are acidic, and </span>pH<span>  higher than </span>7<span> basic ones. 

5) </span><span>The acid dissociation constant for an acid dissolved in water is equal to the equilibrium constant. I consider this option correct because we can obtan </span><span>Kw only when dealing with Kb, and we can conclude that the hydrolysis constant of the conujugate base. 

6) </span>A 0.12 M solution of an acid that ionizes only slightly in solution would be termed dilute and weak. You can determine it depending on its concentration. Such value as 0.12M usually defined as a dilute solution of a weak acid due to the fact that acid represents its <span>partial ionization which is a direct characteristic of a weak acid.
 
7) To solve this task we should appeal to H</span>enry's law that says<span> the solubility of a gaz is proportional to its partial pressure. And according to this we can understand that </span>202kPa is the half of 404kPa which means that the needed solubility must be divided by <span>2 7.5/2=3.75 g/L and that's all.

8) I think that the most important points which best show </span><span>how the addition of a solute affects the boiling point, the freezing
point, and the vapor pressure of the solvent are : BOILING: a</span>dditional attractive forces can only exist between solute and solvent and in order to boil they must be overcome for the solution;we should add KE to overcome the forces. FREEZING : to freeze we have to withdrawn KE as the solute particles are surrounded by solvent molecules. VAPOR : WHen <span>solvent shells are being formed  the solute particles reduces the number of solvent particles that have sufficient KE to vaporize.</span>
<span>
9) </span>[H+][OH-]= Kw = 1.0 * 10^-14
[H+]= Kw/ [OH-]= 1.0x 10^-14 / 1 x 10^-11 =1 x 10^-3 mol/L &#10;&#10;pH = - log [H+]= - log 1 x 10^-3 = 3
Since we got Ph of 3 in a result we can define solution as an acidic one, as I mentioned before.

10) Since the formula of the given acid is HA it undergoes like that :<span> HA<=> H+ + A- .
</span><span>ka = [H][A] / [HA].
Now we have only </span>[H+] and to go further you need to write  <span>electroneutrality equation for the reaction :
</span>[H+] = [OH-] + [A-]  (since [H]>>>[OH]), then 
<span>[H+] = [A-] 
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Ct = 0.5M = [A-] + [HA] 
<span>[HA] = 0.5 - [A-] = 0.5 - [H+] 
</span>Finally here is what we have done and get : 
ka = [H]^2 / (0.5 - [H+]) &#10;
ka = 0.0001*0.0001/(0.5-0.0001) = 2.00x10^-8

11) The main points that are common for acids : they form Hydrogen ions when dissloved in water, - Ex. Vinegar and Lemon, Ph >7, they have <span>Increased hydrogen ions (H+). The facts about bases : they r</span>educe the concentration of hydgoren ions in a solution which is opposite to asids,<span>- Ex. Antiacid,and Ammonia ,</span>Ph valuse above 7, they form hydrogen (OH-).
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