All categories

4 years ago

Determine the pH of (a) a 0.40 M CH3CO2H solution, (b) a solution that is 0.40 M CH3CO2H and 0.20 M NaCH3CO2

Chemistry

1 answer:

elena-s [515]4 years ago

7 0

Answer:

a) pH = 2.573

b) pH = 4.347

Explanation:

a) weak acid: CH3COOH

CH3COOH + H2O ↔ CH3COO- + H3O+

∴ Ka = 1.8 E-5 = [H3O+][CH3COO-] / [CH3COOH]

∴ C CH3COOH = 0.40 M

mass balance:

⇒ 0.40 M = [CH3COO-] + [CH3COOH].........(1)

charge balance:

⇒ [H3O+] = [CH3COO-].........(2)

(2) in (1):

⇒ [CH3COOH] = 0.40 - [H3O+]

replacing in Ka:

⇒ Ka = 1.8 E-5 = [H3O+]² / ( 0.40 - [H3O+] )

⇒ [H3O+]² = 7.2 E-6 - 1.8 E-5[H3O+]

⇒ [H3O+]² + 1.8 E-5[H3O+] - 7.2 E-6 = 0

⇒ [H3O+] = 2.6743 E-3 M

∴ pH = - Log [H3O+]

⇒ pH = 2.573

b) balanced reations:

CH3COONa + H2O → Na+ + CH3COO-
CH3COOH + H2O ↔ CH3COO- + H3O+

∴ C CH3COOH = 0.40 M

∴ C CH3COONa = 0.20 M

mass balanced:

⇒ C CH3COOH + C CH3COONa = [CH3COO-] + [CH3COOH]

⇒ 0.60 = [CH3COO-] + [CH3COOH]......(1)

charge balanced:

⇒ [H3O+] + [Na+] = [CH3COO-]

∴ [Na+] = 0.20 M

⇒ [H3O+] + 0.20 M = [CH3COO-]........(2)

(2) in (1):

⇒ 0.60 M = ( [H3O+] + 0.20 ) + [CH3COOH]

⇒ [CH3COOH] = 0.40 - [H3O+]

replacing in Ka:

⇒ 1.8 E-5 = ([H3O+])([H3O+] + 0.20) / (0.40 - [H3O+])

⇒ 7.2 E-6 - 1.8 E-5[H3O+] = [H3O+]² + 0.20[H3O+]

⇒ [H3O+]² + 0.20[H3O+] - 7.2 E-6 = 0

⇒ [H3O+] = 4.499 E-5 M

⇒ pH = 4.347

You might be interested in

sarah measures out 151 grams of SO2. how many moles is this? Express your answer to three significant figures.

svp [43]

150 g SO₂ = 2.36 mol SO₂

M_r = 32.06 + 2×16.00 = 32.07 + 32.00 = 64.06

Moles of SO₂ = 151 g SO₂ × [1 mol SO₂/64.06 g SO₂] = 2.36 mol SO₂

4 0

3 years ago

Two chemist are trying to determine if their water sample is a mixture or pure substance. In their investigation they first filt

Effectus [21]

The correct answer is option B. Dirty water is a mixture of solid particles and liquid. It is both a mixture and pure substance.

The dirty water sample has both gravel and liquid water in it. After filtration the gravel is removed so the water sample looks clearer than before filtration. Liquid water is a pure substance because it is a compound that is made up of elements hydrogen and oxygen. Now the gravel is only physically combined with the liquid water, thus giving the water sample properties of a mixture. And like any mixture, gravel is physically separated through filtration from the liquid water.

Thus the water sample of the chemists is both a mixture and pure substance.

8 0

4 years ago

Which element is most reactive and why? Fe Mg Pb Zn

murzikaleks [220]

Answer:

Magnesium is the most reactive element. it is higher than the other elements (Fe, Pb, Zn) in the electrochemical series

3 0

3 years ago

6 How many moles are in a 321 g sample of magnesium?

Tatiana [17]

Answer:

13.4mol of Mg

Explanation:

Given parameters:

Mass of magnesium = 321g

Unknown:

Number of moles = ?

Solution:

The number of moles of a substance is given as;

Number of moles = $\frac{mass}{molar mass}$

Molar mass of Mg = 24g/mol

Insert the parameters and solve;

Number of moles = $\frac{321}{24}$ = 13.4mol of Mg

3 0

3 years ago

In nematode worms, a gene that codes for an ATPase has two alternatives for exon 4 and three alternatives for exon 7. How many d

Artyom0805 [142]

Answer:

6 different forms of the protein could be made.

Explanation:

For the given nematode worm, 6 different forms of the protein could be made. This is because of the alternative splicing that will produce 6 kinds of mRNAs. We have 2 different forms for the exon 4 while we have 3 differen forms for the exon 7. Therefore, we have a total of (2*3) 6 different forms of the protein for the given nematode worm.

4 0

4 years ago