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Ilya [14]
3 years ago
8

A chemist titrates 150.0 mL of a 0.2653 M carbonic acid (H2CO3) solution with 0.2196 M NaOH solution at 25 °C. Calculate the pH

at equivalence. The pKa of carbonic acid is 3.60
Chemistry
1 answer:
xxTIMURxx [149]3 years ago
6 0

Answer:

9.3

Explanation:

This is long and complicated so get ready

We are going to use the conjugate base of carbonic acid with water to make carbonic acid and OH- (Na is simply a spectator ion and is irrelavent here)

Let the conjugate base be A- and Carbonic acid be HA

A- + H20 ⇄ HA + OH-

To find the concentration of A- we must find the concentration of the reactants given. We know this will be equal because it is a strong base and all of it disassociates.

to get moles of acid we take the concentration and multiply by liters to cancel

.2653 x .150 = .039795 mol HA

Because it is at equivalence point we know the moles will be equal. We are given the concentration so we only have to solve for liters

We plug it into the equation and found: .181 L

Now use moles and combined volums to fins concentrarion which is .120 M

Now plug that use the Ka converted to Kb to find the cincentrations of HA and OH-

Ka is (10^-3.60) = 2.4E-4

Kb x Ka is 10^-14

Kb = 3.98E-11

Now we know Kb = [HA] [OH] / [A-]

Solve for this through algebra by using x for the values you dont know

youll find x^2 = 3.3E-10

X = 1.8 E -5

this is the OH- concentration

-log [oh] = pOH

pOH = 4.73

We know 14-pOH = ph so pH= 9.3

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How many grams of sodium sulfide can be produced when 45.3 g Na react with 105 g S?
RoseWind [281]
The chemical reaction would be as follows:

<span>2Na + S → Na2S

We are given the amount of the reactants to be used in the reaction. We use these to calculate the amount of product. We do as follows:

45.3 g Na ( 1 mol / 22.99 g ) = 1.97 mol Na
105 g S ( 1 mol / 32.06 g ) = 3.28 mol S

The limiting reactant would be Na. We calculate as follows:

1.97 mol Na ( 1 mol Na2S / 2 mol Na ) (78.04 g / mol ) = 76.87 g Na2S produced</span>
8 0
3 years ago
How are the following aspects of a reaction affected by the addition of a catalyst? 1) activation energy of the reverse reaction
snow_tiger [21]

These are four questions and four answers.

Answers:

1) activation energy of the reverse reaction

     b. Decreased

2) Rate of the forward reaction

    a. Increased

3) Rate of the reverse reaction

    a. Increased

4) Activation energy of the forward reaction

    b. decreased

Explanation:

<em>Activarion energy</em> is the energy required by the reactants to form the intermediate transition state and become products.

<em>Catalysts</em> are substances that change the path of the chemical reactions, lowering the activation energy, and thus speeding up the rate of the reactions, since the products can reach the new lower activation energy faster.

The equilibrium reactions are the chemical process in which two reactions, the <em>forward and the reverese reactions</em>, occur simultaneously and at the same rate.  The equlibrium reactions may be represented by:

  • A ⇄ B

Where A → B is the direct or forward reaction, and A ← B is the reverse reaction (note the inversed arrow, from right to left).

For the direct reaction A represents the reactants and B represents the products. On the other hand, B represents the reactants and A represents the reactants of the reverse reaction and A. This, is A is the reactant of the forward reaction and the product of the reverse reaction, while B is the reactant of the reverse reaction and the product of the forward reaction.

Since, <em>the addition of a catalyst</em> lowers the activation energy of the process, the new activation energy is lower for both the forward and the reverse reaction, meaning that:

1. <em>The activation energy of the reverse reaction is decreased</em> (option b. of the first question)

2.<em> The rate of the forward reaction is increased</em> (option a. of the second question)

3. <em>The rate of the reverse reaction is increased</em> (option a. of the third question).

4. <em>Activation energy of the forward reaction is decreased</em> (option b. of the fourth question).

In summary, the addition of a catalyst decreases the activation energy for both forward and reverse reactions, and increases the rate of both forward and reverse reactions.

3 0
3 years ago
Read 2 more answers
What type of bonds are these?
gulaghasi [49]
Jeez this is middle school really. covalently bond
3 0
3 years ago
If the same amount of heat is added to 5.00 g samples of each of the metals below, which metal will experience the smallest temp
Y_Kistochka [10]

Answer: -

Lower the specific heat capacity of the metal, more the amount of heat would be required to raise the temperature to the same extent.

So for the same amount of heat added to 5.00 g samples of metals, the metal with the lowest specific heat capacity would experience the smallest temperature change.

For example, if the elements are Al, Au ,Cu and Fe, then Au would experience the smallest temperature change due to least specific heat capacity.

5 0
3 years ago
A piece of magnesium is in the shape of a cylinder with a height of 6.62 cm and a diameter of 2.34 cm. If the magnesium sample h
frez [133]

Answer:

0.600 g/cm³

Explanation:

Step 1: Given data

  • Height of the cylinder (h): 6.62 cm
  • Diameter of the cylinder (d): 2.34 cm
  • Mass of the cylinder (m): 17.1 g

Step 2: Calculate the volume of the cylinder

First, we have to determine the radius, which is half of the diameter.

r = d/2 = 2.34 cm/2 = 1.17 cm

Then, we use the formula for the volume of the cylinder.

V= π × r² × h

V= π × (1.17 cm)² × 6.62 cm

V = 28.5 cm³

Step 3: Calculate the density (ρ) of the sample

The density is equal to the mass divided by the volume.

ρ = m/V

ρ = 17.1 g/28.5 cm³

ρ = 0.600 g/cm³

8 0
3 years ago
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