Is Naf A Strong Base
Salts
A salt is an ionic compound formed by the reaction between an acid and a base.� Salts are potent electrolytes that dissociate completely in water.� This dissolution of salts in water frequently affects the pH of a solution.�
Salts that produce Neutral solutions
At the beginning of the semester, nosotros talked about acid-base neutralization reactions.� We adamant that if equimolar amounts of strong acids and bases were mixed, the products were water and salts.� Starting with 100.00 mL of 0.i One thousand NaOH, nosotros were able to calculate how much how much 2.00 M nitric acid, HNOthree, a strong acid, would be needed to neutralize the strong base.�
100.00 mL = 0.100 L ten 0.1 mol NaOH = i.00 ten 10-two mol
50
Neutralization of 1.00 x 10-two mol
������� 1.00 x x-2 mol H+ � 2.00 mol HNO3 = 5.00 x 10-three 50 HNO3
50
This reaction would produce 1.00 10 x-2 moles of water, and one.00 10 10-2 moles of Na+ (aq) and NO3 - (aq) ions in solution.� Their concentrations would be: 1.00 x ten-2 moles/(0.100L + 0.050L) = six.67 x 10-2 M.� Removal of the h2o, evaporation, would pb to the formation of NaNO3 (due south), a common salt.
When sodium nitrate dissolves in water, it dissociates as shown beneath:
NaNO3 (s) + H2O (l) " Na+ (aq) + NO3 - (aq)
Neither of the products, Na+ (aq) nor NOthree - (aq), will donate or take protons.� Na+ is the conjugate acid of the strong base, NaOH.� The Strong bases have conjugate acids of negligible acidity. The strong base of operations, NaOH, dissociates completely in water.� The opposite reaction does non occur.� The species NO3 - is the conjugate base of the strong acid, HNO3.� Over again, the dissociation of HNO3 in water goes to completion, and NO3 - will not take a proton.� It has no basic action.�� When working acid/base of operations bug, continue an centre out for the potent acids and bases, but too for their conjugates, like I-, Cl-, Br-, ClOfour -, NO3 -� and 1000+, Li+, Ca2+, etc.� Whatsoever combination of these anions and cations will produce neutral solutions.� HSO4 -, the cohabit base of the strong acid, HiiThen4, is an exception.� Information technology is itself a weak acid, with a Grand a = 1.iii x ten-2.
Salts that produce Basic solutions
Weak acids tin be neutralized by stiff bases to form water and salts.��� For example, 100.00 mL of a 0.050 M solution of HF could exist reacted with ane.00 K NaOH.� As nosotros have just learned, HF, a weak acid, does not dissociate completely in h2o.
HF (aq) D H+(aq) + F- (aq)���� M a = 1.five x x-11
How can a strong base of operations neutralize the HF completely, when but a small portion of the acid exists in the ionized course?� LeChatelier's Principle.� Only a small amount of H+ exists in solution.� It volition react with the
Equally in the strong acid/strong base calculation, shown above, the titration of a weak acid and strong base of operations can too exist quantified by setting the number of moles of OH- added to the number of moles of H+ in the acrid.� Addition of the strong base of operations will drive the complete dissociation of even a weak acrid.� In this instance,
����������������� 100.00 mL x 0.050 mol �HF = 5.00 x ten-3 mol HF
50
This will react with 5.00 x 10-3 mol NaOH.
�v.00 x 10-3 mol NaOH � mol NaOH = five.00 x 10-three Fifty NaOH
������ L
This volition produce v.00 x 10-3 moles of water and 5.00 x 10-3 moles of� Na+ (aq) and F- (aq).� NaF is the salt formed in this neutralization reaction
A large group of Br�nsted bases consists of the anions of weak acids.� For example, F- is the conjugate base of operations or the weak acrid, HF.�
In water, NaF (s) will dissolve to produce Na+ (aq), the conjugate base of a potent acid, which will not react with h2o.� However, F- will behave like a Br�nsted base of operations, and take a proton from water.
F- (aq) + H2O (l) D HF (aq) +
This is called a hydrolysis reaction, because a molecule of h2o is broken up.�
Why does this happen?� Remember that HF was characterized equally a weak acid.� Near of the HF, in water, exists in the undissociated form, HF.� A small fraction of the HF molecules will donate their protons to water, to class H3O+.�
HF (aq) + HtwoO (l) D HiiiO+ (aq) + F- (aq)
The hydronium ion, H3O+, is the strongest acid that tin exist in h2o.� The equilibrium will strongly favor the reactant side, since H3O+ is a much stronger acid than HF, with a much stronger trend to donate a proton.� When the salt, NaF, is dissolved in water, the F- ion is created.�
F- (aq) + H2O (50) D HF (aq) +
In this reaction,
Example 1 A solution is made by adding solid NaClO to plenty water to make 2.0 L of solution.� If the solution has a pH of 10.50, how many moles of NaClO were added?� The G b of ClO- = 3.iii ten x-seven.
1.� What reaction is taking place?� NaClO is a table salt, which will dissolve completely in h2o, to form Na+ and ClO- .� This second species, hypochlorite, ClO- , is the cohabit base of the weak acid, HClO.� And so, this is a weak base equilibrium problem, like the previous example.�
ClO- (aq) + H2O (l) D HClO (aq) +
�������������������� �������������������������������������������������������������������������� [ClO-]
two.� We know [H+]eq and K b.
3.� Since this is a weak base problem, nosotros demand to know the [
pH = 10.50 = 14 � pOH��������� pOH = 3.five������ [
����������������������� [ClO-] (G)������ [HClO](M)����� [
Initial��������������� X�������������������� 0.00���������������� 0.00
Change������������ -x�������������������� +ten������������������� +x
Equilibrium������ 10 � 10��������������� ten��������������������� 10
Yard b = iii.3 ten x-7 = (x)(x) �= (iii.16 10 10-iv)2 �� 10 = 0.thirty Thou
��������������������������� X � ten������������� X
4.� The assumptions are O.One thousand.� The dissociation is (three.16 ten 10-4/.3) 10 100 = 0.one% and the [OH-] from the base is much greater than the [
In this example, it was important to recognize that ClO- was the conjugate base of a weak acid.�
HClO (aq)� D ClO- (aq) + H+ (aq)������������������������������ Chiliad a = [ClO-] [H+]
����������������������������������������������������������������������������������� ���������� [HClO]
ClO- (aq) + HiiO (l) D HClO (aq) +
����������������������������������������������������������������������������������� � �[ClO-]
Adding the two equations gives:
HClO (aq) + ClO- (aq) + H2O (fifty) D ClO- (aq) + H+ (aq) + HClO (aq) +
�HiiO (l) D H+ (aq) +
In general, ������ reaction one + reaction two = reaction three ������� K i ten
The relationship between acids and their conjugate bases is shown, below, for some common acids and bases.
Grand a������������������������������������������ Acid ����������������������������������������������������� Base��������������������������� Yard b
strong acid������������������� HNOthree, Hello, HCl, etc���������������� NO3, I-, Cl-, etc����������� negligible basicity
half dozen.8 x x-4 �������������������� HF������������������������������������������ F- �������������������������������� i.5 10 ten-11
i.8 ten x-5 �������������������� CH3COOH����������������������������� CH3COO- ������������������� v.6 10 10-10
4.3 x 10-seven �������������������� H2COiii ������������������������������������ HCO3 - ������������������������� 2.iii ten ten-8
v.vi x 10-10 ������������������� NH4 + ��������������������������������������� NH3 ���������������������������� 1.8 x 10-five
5.6 ten 10-11 ������������������� HCO3 - ������������������������������������� CO3 two- �������������������������� one.8 10 10-four
negligible acidity����������� Li2O, NaOH��������������������������� O2-,
The K b can always be calculated from the K a and vice versa.� K a x K b = K w = 1.0 x ten-xiv.�
Salts that produce Acidic solutions
When a strong acrid is used to neutralize a weak base of operations, the reaction again goes to completion.� Although the weak base is largely undissociated, as soon as the OH- it produces is reacted with the added H+ from the strong acrid, more of the base will dissociate to course additional production.� In this way, the reaction is driven to completion.�
When a salt derived from a strong acrid and a weak base of operations dissolves in water, the solution becomes acidic.� For instance:
NHivCl (south) + H2O (l) D NH4 + (aq) + Cl- (aq)
The Cl- has no affinity for a proton, it is the conjugate base of operations of the strong acid, HCl.� However, the ammonium ion, NH4 + , is the conjugate acrid of the weak base, ammonia, and it will hydrolyze water:
NH4 + (aq) + H2O (l) D NH3 (aq) + H3O+ (aq)
Since this reaction produces protons (H3O+), the pH of the solution will decrease.
Case 2� What are the percent hydrolysis and pH of a 0.10 M NHivCl solution?
ane.� NH4Cl is the salt formed in the reaction between a strong acid (HCl) and a weak base (NH3).� Only the cation, NH2 + , volition hydrolyze water.�
NH4Cl (s) + HtwoO " NH4 + (aq) + Cl- (aq)
At that place is a complete dissociation in h2o, since this is a strongly electrolytic common salt.� Once in solution, the Cl- becomes a spectator ion.� The reaction itself only involves the ammonium ion.
NH4 + (aq) + H2O (l) D NH3 (aq) + H3O+ (aq)
two.� The G b for NH3 = one.viii x 10-5, then the Thousand a = One thousand w / K b = 5.6 x x-ten.
3.� ������������������������������ [NH4 +] (K)����� [NHiii] (M)������� [H+] (Grand)
����������� Initial��������������� 0.10���������������� 0.00���������������� 0.00
����������� Alter������������ -x�������������������� +10������������������� +x
����������� Equilibrium������ 0.10 � x���������� x��������������������� x
����������� K a =�� ���� x2 � �= v.6 x x-10 � 10 = 7.5 ten 10-6 = [H+]
����������������������� 0.10 �x�����������
�����������
����������� To check the approximation� 7.5 x x -6 x 100 = 0.0075%� << 5%.� This is likewise the per centum hydrolysis.
��������������������������������������������������������� 0.x
����������� pH = -log (7.5 x 10-6) = five.12
Salts in which both the Cation and Anion hydrolyze h2o
So far we accept looked at salts of stiff acids and strong bases (neutral solution), salts of weak acids and stiff bases (basic solutions) and salt of weak bases and potent acids (basic solutions).� what about salts from weak acids and weak bases, similar NHfourNOii, or NHfourCN?� The mathematics is fairly complex, then we will only describe qualitatively what happens.�
What would happen in a reaction of NHivCN and water, for instance.� NHiv + is the conjugate acids of the weak base, NH3, and CN- is the cohabit base of operations of the weak acrid, HCN.��
Write out the reactions of each of the salt components with water.
NHiv + (aq) + H2O (l) D NH3 (aq) + HiiiO+ (aq) K a = 5.6 x x-10
CN- (aq) + H2O (l) D HCN (aq) +
A comparison of the equilibrium constants, shows that the G b >> Thousand a, so NH4CN will form a basic solution.
Amphoteric Salts
These are salts that can either take or donate a proton in h2o.� An case is the bicarbonate ions, HCOiii -.� And then, if a solution of sodium bicarbonate (baking soda) is prepared, the Na+ becomes a spectator ion, and the bicarbonate tin undergo two dissimilar reactions:
HCO3 - (aq) + H2O(l) D H3O+ (aq) + COthree 2- (aq)��������� K a = v.6 x 10-xi
HCOiii - (aq) + H2O (l) D H2CO3 (aq) +
Since K b � >> K a, the second reaction volition proceed, giving a basic solution.�
Is Naf A Strong Base,
Source: http://butane.chem.uiuc.edu/cyerkes/Chem102AEFa07/Lecture_Notes_102/Lecture%2024-102.htm
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