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3 years ago

What is the ph of an aqueous solution with [h3o+] = 2×10−14 m ?

1 answer:

N76 [4]3 years ago

4 0

The general formula for finding pH is:

$pH=-log[ H _{3}O ^{+}]$ -> This equation could also work with H+.

So using the formula and plugging in the hydronium ion concentration:

$pH=-log(2* 10^{-14}M)$

$pH=13.7$

So the solution has a pH of 13.7.

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Consider the titration of 100.0 mL of 0.280 M propanoic acid (Ka = 1.3 ✕ 10−5) with 0.140 M NaOH. Calculate the pH of the result

Murljashka [212]

Answer:

(a) 2.7

(b) 4.44

(d) 5.363

(e) 5.570

(f) 12.30

Explanation:

Here we have the titration of a weak acid with the strong base NaOH. So in part (a) simply calculate the pH of a weak acid ; in the other parts we have to consider that a buffer solution will be present after some of the weak acid reacts completely the strong base producing the conjugate base. We may even arrive to the situation in which all of the acid will be just consumed and have only the weak base present in the solution treating it as the pOH and the pH = 14 -pOH. There is also the possibility that all of the weak base will be consumed and then the NaOH will drive the pH.

Lets call HA propanoic acid and A⁻ its conjugate base,

(a) pH = -log √ (HA) Ka =-log √(0.28 x 1.3 x 10⁻⁵) = 2.7

(b) moles reacted HA = 50 x 10⁻³ L x 0.14 mol/L = 0.007 mol

mol left HA = 0.28 - 0.007 = 0.021

mol A⁻ produced = 0.007

Using the Hasselbalch-Henderson equation for buffer solutions:

pH = pKa + log ((A⁻/)/(HA)) = -log (1.3 x 10⁻⁵) + log (0.007/0.021)= 4.89 + (-0.48) = 4.44

mol HA left = 0.028 -0.014 = 0.014 mol

mol A⁻ produced = 0.014

pH = -log (1.3 x 10⁻⁵) + log (0.014/0.014) = 4.886

(d) mol HA reacted = 150 x 10⁻³ L x x 0.14 mol/L = 0.021 mol

mol HA left = 0.028 - 0.021 = 0.007

mol A⁻ produced = 0.021

pH = -log (1.3 x 10⁻⁵) + log (0.021/0.007) = 5.363

(e) mol HA reacted = 200 x 10⁻³ L x 0.14 mol/L = 0.028 mol

mol HA left = 0

Now we only a weak base present and its pH is given by:

pH = √(kb x (A⁻) where Kb= Kw/Ka

Notice that here we will have to calculate the concentration of A⁻ because we have dilution effects the moment we added to the 100 mL of HA, 200 mL of NaOH 0.14 M. (we did not need to concern ourselves before with this since the volumes cancelled each other in the previous formulas)

mol A⁻ = 0.028 mOl

Vol solution = 100 mL + 200 mL = 300 mL

(A⁻) = 0.028 mol /0.3 L = 0.0093 M

and we also need to calculate the Kb for the weak base:

Kw = 10⁻¹⁴ = ka Kb ⇒ Kb = 10⁻¹⁴/1.3x 10⁻⁵ = 7.7 x 10⁻ ¹⁰

pH = -log (√( 7.7 x 10⁻ ¹⁰ x 0.0093) = 5.570

(f) Treat this part as a calculation of the pH of a strong base

moles of OH = 0.250 L x 0.14 mol = 0.0350 mol

mol OH remaining = 0.035 mol - 0.028 reacted with HA

= 0.007 mol

(OH⁻) = 0.007 mol / 0.350 L = 2.00 x 10 ⁻²

pOH = - log (2.00 x 10⁻²) = 1.70

pH = 14 - 1.70 = 12.30

4 0

2 years ago

Aspirin that has been stored for a long time may give a vinegar like odour and give a purple colour with FeCl3. What reaction wo

iVinArrow [24]

Answer:

See explanation

Explanation:

The IUPAC name of aspirin is 2-Acetoxybenzoic acid. It is composed of an acetoxy moiety and a benzoic acid moiety.

The compound can be hydrolysed under prolonged storage conditions to yield acetic acid which causes the vinegar like odour.

Also, one of the products of this hydrolysis bears a phenol group which reacts with FeCl3 to give a purple color.

3 0

3 years ago

How does the average velocity of molecules in a high-temperature gas compare to the average velocity of molecules of the same ga

IrinaK [193]

Answer:lower temp molecules act slower so they come closer together and heated molecules are more spaced out that is why when you put an ice cube in a hot pan the ice melts and turns into a liquid due to heat the molecules space out

Explanation:

8 0

3 years ago

The organic compound di‑n‑butyl phthalate, C 16 H 22 O 4 ( l ) , C16H22O4(l), is sometimes used as a low‑density ( 1.046 g ⋅ mL

damaskus [11]

Answer:

36.63 Torr

Explanation:

You need to use two expressions, one for pressure and the other with the relation of density and height of the column.

For the pressure:

P = h * d * g (1)

h is height.

d density

g gravity

The second expression put a relation between the densities and height of the column so:

d1/d2 = h1/h2 (2)

let 1 be the phthalate, and 2 the mercury.

Let's calculate first the relation of density:

d1/d2 = 13.53 / 1.046 = 12.93

Now with the first expression, we can calculate the pressure so:

P = hdg

We have two compounds so,

h1d1g = h2d2g ---> gravity cancels out

From here, we can solve for h2:

h2 = h1*(d1/d2)

replacing:

h2 = 459 / 12.53

h2 = 36.63 mm

1 mmHg is 1 torr, therefore the pressure of the gas in Torr would be 36.63 Torr

8 0

3 years ago

State two conditions necessary for an esterification reaction to take place

nadya68 [22]

Explanation:

Esterification occurs when a carboxylic acid reacts with an alcohol. This reaction can only occur in the presence of an acid catalyst and heat. It takes a lot of energy to remove the -OH from the carboxylic acid, so a catalyst and heat are needed to produce the necessary energy.

4 0

3 years ago

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