Identify the correct statement regarding the strength of chemical bonds.

A 420 mL sample of a 0.100 M formate buffer, pH 3.75, is treated with 7 mL of 1.00 M KOH. What is the pH following this addition

Art [367]

Answer: The pH of the resulting solution will be 3.60

Explanation:

Molarity is calculated by using the equation:

$\text{Molarity}=\frac{\text{Moles}}{\text{Volume}}$ ......(1)

We are given:

Molarity of formic acid = 0.100 M

Molarity of potassium formate = 0.100 M

Volume of solution = 420 mL = 0.420 L (Conversion factor: 1 L = 1000 mL)

Putting values in equation 1, we get:

$\text{Moles of formic acid}=(0.100mol/L\times 0.420L)=0.0420mol$

$\text{Moles of potassium formate}=(0.100mol/L\times 0.420L)=0.042mol$

Molarity of KOH = 1.00 M

Volume of solution = 7 mL = 0.007 L

Putting values in equation 1, we get:

$\text{Moles of KOH}=(1mol/L\times 0.007L)=0.007mol$

The chemical equation for the reaction of formic acid and KOH follows:

$HCOOH+KOH\rightleftharpoons HCOOK+H_2O$

I: 0.042 0.007 0.042

C: -0.007 -0.007 +0.007

E: 0.035 - 0.049

Volume of solution = [420 + 7] = 427 mL = 0.427 L

To calculate the pH of the acidic buffer, the equation for Henderson-Hasselbalch is used:

$pH=pK_a+ \log \frac{\text{[conjugate base]}}{\text{[acid]}}$ .......(2)

Given values:

$[HCOOK]=\frac{0.049}{0.427}$

$[HCOOH]=\frac{0.035}{0.427}$

$pK_a=3.75$

Putting values in equation 2, we get:

$pH=3.75-\log \frac{(0.049/0.427)}{(0.035/0.427)}\\\\pH=3.75-0.146\\\\pH=3.60$

Hence, the pH of the resulting solution will be 3.60

6 0

3 years ago

Use the graph to answer these questions. For numerical answers, use correct significant digits.

kykrilka [37]

Answer:

1. Letter  A shows the overall enthalpy of reaction

2. which is equal to kJ 2,538.90kJ

3. Letter  B shows the activation energy for the reaction

4. The activated complex is represented by letter C

Explanation:

1. Letter __ shows the overall enthalpy of reaction

The overall enthalpy of reaction is equal to the change of enthalpy of the substances:

Enthalpy of reaction = ∑ enthalpy of the products - ∑enthalply of the reactants.

The products are shown of the right side of the diagram. They are C₆H₁₂O₆(g) and 6O₂(g).

The reactants are shown of the left side of the diagram. They are 6CO₂(g) and 6H₂O(g).

The arrow labeled A shows the difference between the enthalpies of the products and the reactants; thus this shows the overall enthalpy of reaction.

2. which is equal to kJ__

You must subtract the enthalpy of the iniital state (reactants) from the enthalpy of the final state (products).

Overall enthalpy of reaction = - 1,273.02kJ - ( - 3,811.92kJ)

Overall enthalpy of reaction = 2,538.90kJ

This is a positive change indicating the reaction is endothermic.

3. Letter___shows the activation energy for the reaction

The activation energy is the energy that the reactants must gain for the reaction occurs.

Thus, it is the difference between the maximum energy, indicated by the label C on the graph, and initial state.

That is shown by the arrow labeled B: the reactants must gain the amount of energy indicated by the arrow labeled B to reach the energy of the state labeled C.

4. The activated complex is represented by ____

The activated complex is the intermediate compound formed while the reactants are breaking their bonds and new bonds start to form the products. It is also called transition state.

The activated complex is on the top of the energy diagram because it hat the highest energy. The formation of the activated complex always requires energy (it is an endothermic process). Once it is formed, energy is released and the reactants are formed (this part is exothermic).

Thus, the activated complex is labeled with the letter C.

8 0

4 years ago

Read 2 more answers

How many grams of magnesium are needed to completely react

Verizon [17]

97.22 grams of magnesium is needed.

Explanation:

The molar ratio of Mg to O2 to make MgO is 2:1

Here, we have 2 moles of O2, therefore we need 4 moles of Mg.

1 mol of Mg = 24.305 g

Therefore