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The odor of vinegar is due to the presence of acetic acid, CH 3 CO 2 H, a weak acid. List, in order of descending concentration, all of the ionic and molecular species present in a 1- M aqueous solution of this acid.

[H 2 O]>[CH 3 CO 2 H]> [ H 3 O + ] [ CH 3 CO 2 ] >[OH ]

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Household ammonia is a solution of the weak base NH 3 in water. List, in order of descending concentration, all of the ionic and molecular species present in a 1- M aqueous solution of this base.

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Explain why the ionization constant, K a , for H 2 SO 4 is larger than the ionization constant for H 2 SO 3 .

The oxidation state of the sulfur in H 2 SO 4 is greater than the oxidation state of the sulfur in H 2 SO 3 .

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Explain why the ionization constant, K a , for HI is larger than the ionization constant for HF.

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Gastric juice, the digestive fluid produced in the stomach, contains hydrochloric acid, HCl. Milk of Magnesia, a suspension of solid Mg(OH) 2 in an aqueous medium, is sometimes used to neutralize excess stomach acid. Write a complete balanced equation for the neutralization reaction, and identify the conjugate acid-base pairs.

Mg ( OH ) 2 ( s ) + 2HCl ( a q ) Mg 2+ ( a q ) + 2 Cl ( a q ) + 2H 2 O ( l ) BB BA CB CA

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Nitric acid reacts with insoluble copper(II) oxide to form soluble copper(II) nitrate, Cu(NO 3 ) 2 , a compound that has been used to prevent the growth of algae in swimming pools. Write the balanced chemical equation for the reaction of an aqueous solution of HNO 3 with CuO.

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What is the ionization constant at 25 °C for the weak acid CH 3 NH 3 + , the conjugate acid of the weak base CH 3 NH 2 , K b = 4.4 × 10 −4 .

K a = 2.3 × 10 −11

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What is the ionization constant at 25 °C for the weak acid ( CH 3 ) 2 NH 2 + , the conjugate acid of the weak base (CH 3 ) 2 NH, K b = 5.9 × 10 −4 ?

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Which base, CH 3 NH 2 or (CH 3 ) 2 NH, is the stronger base? Which conjugate acid, ( CH 3 ) 2 NH 2 + or (CH 3 ) 2 NH, is the stronger acid?

The stronger base or stronger acid is the one with the larger K b or K a , respectively. In these two examples, they are (CH 3 ) 2 NH and CH 3 NH 3 + .

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Which is the stronger acid, NH 4 + or HBrO?

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Which is the stronger base, (CH 3 ) 3 N or H 2 BO 3 ?

triethylamine.

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Predict which acid in each of the following pairs is the stronger and explain your reasoning for each.

(a) H 2 O or HF

(b) B(OH) 3 or Al(OH) 3

(c) HSO 3 or HSO 4

(d) NH 3 or H 2 S

(e) H 2 O or H 2 Te

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Predict which compound in each of the following pairs of compounds is more acidic and explain your reasoning for each.

(a) HSO 4 or HSeO 4

(b) NH 3 or H 2 O

(c) PH 3 or HI

(d) NH 3 or PH 3

(e) H 2 S or HBr

(a) HSO 4 ; higher electronegativity of the central ion. (b) H 2 O; NH 3 is a base and water is neutral, or decide on the basis of K a values. (c) HI; PH 3 is weaker than HCl; HCl is weaker than HI. Thus, PH 3 is weaker than HI. (d) PH 3 ; in binary compounds of hydrogen with nonmetals, the acidity increases for the element lower in a group. (e) HBr; in a period, the acidity increases from left to right; in a group, it increases from top to bottom. Br is to the left and below S, so HBr is the stronger acid.

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Rank the compounds in each of the following groups in order of increasing acidity or basicity, as indicated, and explain the order you assign.

(a) acidity: HCl, HBr, HI

(b) basicity: H 2 O, OH , H , Cl

(c) basicity: Mg(OH) 2 , Si(OH) 4 , ClO 3 (OH) (Hint: Formula could also be written as HClO 4 ).

(d) acidity: HF, H 2 O, NH 3 , CH 4

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Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
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