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13 Dec 2019

1(a)What is the pH of a buffer system that contains 0.26M hydrocyanic acid (HCN) and 0.30M Sodium cyanide? The Ka of HF is 6.2 x 10^-10

1(B)Consider 750mL of the buffer system described above. What are the [HCN] and [CN^-] after 0.080 mol of NaOH is added? What is the pH?

1(c)Consider 500mL of the buffer system described above. What are the [HCN] and [CN^-] after 0.10 mol of HCl is added? What is the pH?

2.A titration of 15mL of boric acid (H₃BO₃) required 22mL of 0.25M Ca(OH)₂ Write the balanced equation for the reaction of boric acid with Ca(OH)₂ and determine how many milligrams of boric acid are present

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Reid WolffLv2

17 Dec 2019

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1. Identify the following substances as a Brønsted-Lowry base, a Brønsted-Lowry acid, or neither.

2.Enter the formulas of the conjugate bases of the following Brønsted-Lowry acids.

$H C l O_{4}$ Express your answer as a chemical formula.

- $({C H}_{3})_{2} {N H}_{2}^{+}$ Express your answer as a chemical formula.

- $H_{2} S$ Express your answer as a chemical formula.

- $H S e O_{3}^{-}$ Express your answer as a chemical formula.

3.Based on the $K_{a}$ values in the table, rank the following solutions in order of decreasing $p H$ : 0.10 $M$ $H C O O H$ , 0.10 $M$ $H F$ , 0.10 $M$ $H_{2} {C O}_{3}$ , 0.10 $M$ ${H S O}_{4}^{-}$ , and 0.10 $M$ ${N H}_{4}^{+}$ .

Rank from highest to lowest. To rank items as equivalent, overlap them.

4.What is the

p H

of a buffer system that contains 0.180

M

hydrocyanic acid

(H C N)

and 0.230

M

sodium cyanide

(N a C N)

? The

p K_{a}

of hydrocyanic acid is 9.31.

Express your answer using two decimal places.

5.Sulfuric acid reacts with water to yield hydrogen sulfate ions and hydronium ions:

$H_{2} S O_{4} + H_{2} O ⇌ H S O_{4}^{-} + H_{3} O^{+}$

Identify as acid,conjugate base,base or conjugate acid.

6.Hydrogen sulfate reacts with water to produce sulfate ions and hydronium ions:

${H S O_{4}}^{-} + H_{2} O ⇌ {S O_{4}}^{2 -} + H_{3} O^{+}$

Identify as acid,conjugate base,base or conjugate acid.

Proteins are complex biological molecules made of smaller molecules called amino acids. Five common amino acids and their

K_{a} K_{\rm a}

values are listed below. Rank them from strongest to weakest acid.

Amino acid	$K_{a} K_{\rm a}$
glutamine	6×10⁻³
arginine	2×10⁻²
threonine	3×10⁻³
tryptophan	4×10⁻³
proline	1×10⁻²

Rank from strongest to weakest acid. To rank items as equivalent, overlap them.

tealdog287

calculate pH if an aqueous solution of 0.200 M acetic acid

1) What is the pH (to nearest 0.01 pH unit) of a solution prepared by mixing 90.0 mL of 0.0509 M NaOH and 60.0 mL of 0.0400 M Ba(OH)2?

2) What is the pH (to nearest 0.01 pH unit) of a solution prepared by mixing 78.0 mL of 0.604 M HCl and 69.0 mL of 0.823 M NaOH?

3) Calculate the pH of each of the solutions and the change in pH to 0.01 pH units caused by adding 10.0 mL of 2.54-M HCl to 470. mL of each of the following solutions.

Change is defined as final minus initial, so if the pH drops upon mixing the change is negative.

a) water

pH before mixing =
pH after mixing=
pH change =

b) 0.178 M C₂H₃O₂^1-

pH before mixing =
pH after mixing=
pH change =

c) 0.178 M HC₂H₃O₂

pH before mixing =
pH after mixing=
pH change =

d) a buffer solution that is 0.178 M in each C₂H₃O₂^1- and HC₂H₃O₂

pH before mixing =
pH after mixing=
pH change =

4) Calculate the change in pH to 0.01 pH units caused by adding 10. mL of 2.60-M NaOH is added to 550. mL of each of the following solutions.

a) water

pH before mixing =
pH after mixing=
pH change =

b) 0.176 M NH₄¹⁺

pH before mixing =
pH after mixing=
pH change =

c) 0.176 M NH₃

pH before mixing =
pH after mixing=
pH change =

d) a buffer solution that is 0.176 M in each NH₄¹⁺ and NH₃

pH before mixing =
pH after mixing=
pH change =

Consider the titration of 30.0 mL of 0.189-M of KX with 0.172-M HCl. The pK_a of HX = 8.59. Give all pH values to 0.01 pH units.

a) What is the pH of the original solution before addition of any acid?

pH =

b) How many mL of acid are required to reach the equivalence point?

V_A = mL

c) What is the pH at the equivalence point?

pH =

d) What is the pH of the solution after the addition of 11.2 mL of acid?

pH =

e) What is the pH of the solution after the addition of 39.6 mL of acid?

pH =

A 4.543-g sample of a solid, weak, monoprotic acid is used to make 100.0 mL of solution. 15.0 mL of this solution was titrated with 0.07921-M NaOH. The pH after the addition of 28.38 mL of base was 5.60, and the equivalence point was reached with the addition of 48.60 mL of base.

a) How many millimoles of acid are in the original solid sample? Hint: Don't forget the dilution.

mmol acid

b) What is the molar mass of the acid?

g/mol

c) What is the pK_a of the acid?

pK_a =

A lot of these are similar problems, so if someone could let me know how to do them then I could probably figure the rest of them out. I was out of class the day we went over this and am completely lost.

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