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2 years ago

Please help this is due soon and I’ll mark you brainiest if you can help

Chemistry

1 answer:

attashe74 [19]2 years ago

7 0

Answer:

I think it's either A or D I'm not sure hope that I helped you.

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A 20.0 mL of 0.27 M solution of the salt NaA has a pH of 8.70.

zlopas [31]

Answer:

a) 3.969

b) 3.489

Explanation:

a) Calculate the pk, value of the acid HA

PH of salt hydrolysis

P $^{H}$ = 1/2 ( pkw + pka + logC )

8.7 * 2 = 14 + log ( 0.27 ) + Pka

∴ Pka = 3.9686 ≈ 3.969

b) Calculate the PH of a solution containing 0.3 M HA and 0.1 M NaA

PH = Pka + log ( salt / acid )

= 3.9686 + log ( 0.1 / 0.3 )

= 3.9686 - 0.48 = 3.489

3 0

2 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

elena-s [515]

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

7 0

3 years ago

Ameadow food chain is shown.

GalinKa [24]

The mouse is a Secondary consumer

7 0

3 years ago

Read 2 more answers

(b) Data has been collected to show that at a given wavelength in a 1 cm pathlength cell, Beer's Law for the absorbance of Co2+

OlgaM077 [116]

Answer : The concentration of a solution with an absorbance of 0.460 is, 0.177 M

Explanation :

Using Beer-Lambert's law :

$A=\epsilon \times C\times l$

where,

A = absorbance of solution

C = concentration of solution

l = path length

$\epsilon$ = molar absorptivity coefficient

From this we conclude that absorbance of solution is directly proportional to the concentration of solution at constant path length.

Thus, the relation between absorbance and concentration of solution will be:

$\frac{A_1}{A_2}=\frac{C_1}{C_2}$

Given:

$A_1$ = 0.350

$A_2$ = 0.460

$C_1$ = 0.135 M

$C_2$ = ?

Now put all the given values in the above formula, we get:

$\frac{0.350}{0.460}=\frac{0.135}{C_2}$

$C_1=0.177M$

Therefore, the concentration of a solution with an absorbance of 0.460 is, 0.177 M

3 0

3 years ago

A sample of a pure substance with a density of 3 g/mL is separated into two pieces. One piece has a mass of 50 g and the other p

pshichka [43]

Answer:

8.3ml

Explanation:

to get volume u have to divide 25g over the density, i rounded to the nearest tenth, if you don't want to then write out the full number with all the decimals

4 0

2 years ago