What would the initial pH of a acetate/acetic acid buffer system (pKa = 4.75) if the concentration of acetate is 1.36 × 10-2 molar and the concentration of acetic acid is 1.64 × 10-1?A.
5.83
B.
3.67
C.
2.08
D.
1.66

Answer:

1. C

2.B

Explanation:

The number of oxygen atoms in 19.3 g of sodium sulfate (Na₂SO₄) is 3.27×10²³ atoms

We'll begin by calculating the number of mole in 19.3 g of sodium sulfate (Na₂SO₄).

Mass of Na₂SO₄ = 19.3 g

Molar mass of Na₂SO₄ = (23×2) + 32 +(16×4)

= 46 + 32 + 64

= 142 g/mol

Mole of Na₂SO₄ =?

Mole = mass / molar mass

Mole of Na₂SO₄ = 19.3 / 142

Mole of Na₂SO₄ = 0.136 mole

Recall:

1 mole of Na₂SO₄ contains 4 moles of O.

Therefore,

0.136 mole of Na₂SO₄ will contain = 0.136 × 4 = 0.544 mole of O

Finally, we shall determine the number of atoms in 0.544 mole of O.

From Avogadro's hypothesis,

1 mole of O = 6.02×10²³ atoms

Therefore,

0.544 mole of O = 0.544 × 6.02×10²³

0.544 mole of O = 3.27×10²³ atoms

Thus, 19.3 g of sodium sulfate (Na₂SO₄) contains 3.27×10²³ atoms of oxygen.

Learn more: brainly.com/question/25115547

Answer:

3.27·10²³ atoms of O

Explanation:

To figure out the amount of oxygen atoms in this sample, we must first evaluate the sample.

The chemical formula for sodium sulfate is Na₂SO₄, and its molar mass is approximately 142.05.

We will use stoichiometry to convert from our mass of Na₂SO₄ to moles of Na₂SO₄, and then from moles of Na₂SO₄ to moles of O using the mole ratio; then finally, we will convert from moles of O to atoms of O using Avogadro's constant.

19.3g Na₂SO₄ · · ·

After doing the math for this dimensional analysis, you should get a quantity of approximately 3.27·10²³ atoms of O.

Answer:

a) Warmer

b) Exothermic

c) -10.71 kJ

Explanation:

The reaction:

KOH(s) → KOH(aq) + 43 kJ/mol

It is an exothermic reaction since the reaction liberates 43 kJ per mol of KOH dissolved.

Hence, the dissolution of potassium hydroxide pellets to water provokes that the beaker gets warmer for being an exothermic reaction.

The enthalpy change for the dissolution of 14 g of KOH is:

Where:

m: is the mass of KOH = 14 g

M: is the molar mass = 56.1056 g/mol

The enthalpy change is:

The minus sign of 43 is because the reaction is exothermic.

I hope it helps you!

Answer:

Ca₃(AsO₃)₂

Explanation:

Sodium arsenite, with the chemical formula Na₃AsO₃, is formed  by the cation Na⁺ and the anion AsO₃³⁻. For the molecule to be neutral, 3 cations Na⁺ and 1 anion AsO₃³⁻ are required.

Calcium arsenite would be formed by the cation Ca²⁺ and the anion AsO₃³⁻. For the molecule to be neutral, we require 3 cations Ca²⁺ and 2 anions AsO₃³⁻. The resulting chemical formula is Ca₃(AsO₃)₂.

Answer:

A solution that is 0.10 M HCN and 0.10 M LiCN

. A solution that is 0.10 M NH3 and 0.10 M NH4Cl

Explanation:

A buffer consists of a weak acid and its conjugate base counterpart. HCN is a weak acid and the salt LiCN contains its counterpart conjugate base which is the cyanide ion. A buffer maintains the pH by guarding against changes in acidity or alkalinity of the solution.

A solution of ammonium chloride and ammonia will also act as a basic buffer. A buffer may also contain a weak base and its conjugate acid.

Answer:

Good buffer systems are:  

A) NH3 + NH4Cl

C) HCN + LiCN

D) HF + NaF

Explanation:

Buffers consist in a mixture of a weak acid with its salt or a weak alkaly with its salt. All buffer systems are conformed by:

1) Weak acid + salt

or

2) Weak alkaly + salt

It is very important these salts come from the weak acid or weak alkaly. It means, the anion of the acid must be the anion in the salt which is going to be part of the buffer system. On the other hand, the cation of the weak alkaly must be the cation of the salt which is going to form the salt in the buffer system.

Then, when we evaluate all options in this exercise, answers are the following:

A) 0.10 M NH3 and 0.10 M NH4Cl. It is a buffer because NH3 (ammonia) is a weak alkaly and NH4Cl is a salt coming from NH3.

Buffer component reactions:

Reaction weak alkaly:   NH3 + H2O <-----> NH4+ + OH-

Reaction salt in water:  NH4Cl ---> NH4+ + Cl-

NH4+ is the cation of the weak alkaly so it must be part of the salt in the buffer system. Then NH4Cl is a salt from NH3.

C) 0.10 M HCN and 0.10 M LiCN. It is a buffer because HCN is a weak acid and LiCN is a salt which is coming from HCN.

Buffer component reactions:

Reaction weak acid:     HCN + H2O <-----> H3O+ + CN-  

Reaction salt in water:  LiCN --> Li+ + CN-

CN- is the anion of the acid, so it must be part of the salt in the buffer system. Then LiCN is a salt from HCN.

D) 0.10 M HF and 0.10 M NaF. It is a buffer because HF is a weak acid and NaF is a salt which is coming from HF.

Buffer component reactions:

Reaction weak acid:      HF + H2O <------> H3O+ + F-

Reaction salt in water:   NaF ---> Na+ + F-

F- is the anion of the weak acid (HF), so it must be part of the salt in th buffer systema. Then NaF is a salt coming from HF.

However option B, it is not a buffer, because it is a mixture of 0.10 M HCN and 0.10 M NaF.    Salt is not coming from the weak acid.

Reaction weak acid:    HCN + H2O <-----> H3O+ + CN-  (anion of the acid is CN-)

Rection salt in water:   NaF --> Na+ + F-  (anion in the salt is F-, not CN-)

Anion of the acid is CN- and the anion in the salt is F- so it is not a salt coming from the weak acid. Then option B it is not a buffer system.

Answer :  The rate for the formation of hydrogen is, 1.05 M/s

Explanation :

The general rate of reaction is,

Rate of reaction : It is defined as the change in the concentration of any one of the reactants or products per unit time.

The expression for rate of reaction will be :

From this we conclude that,

In the rate of reaction, A and B are the reactants and C and D are the products.

a, b, c and d are the stoichiometric coefficient of A, B, C and D respectively.

The negative sign along with the reactant terms is used simply to show that the concentration of the reactant is decreasing and positive sign along with the product terms is used simply to show that the concentration of the product is increasing.

The given rate of reaction is,

The expression for rate of reaction :

The rate of reaction expression is:

As we are given that:

Now we to determine the rate for the formation of hydrogen.

Thus, the rate for the formation of hydrogen is, 1.05 M/s