Calculate the [H+] for<br> (a) black coffee with a pH of 3.59

Anna [14]

Considering the Hess's Law, the enthalpy change for the reaction is 221.8 kJ/mol.

Hess's Law indicates that the enthalpy change in a chemical reaction will be the same whether it occurs in a single stage or in several stages. That is, the sum of the ∆H of each stage of the reaction will give us a value equal to the ∆H of the reaction when it occurs in a single stage.

In this case you want to calculate the enthalpy change of:

C₂H₄ (g) + 6 F₂ (g) → 2 CF₄ (g) + 4 HF (g)

which occurs in three stages.

You know the following reactions, with their corresponding enthalpies:

Equation 1: H₂ (g) + F₂ (g) → 2 HF (g) ∆H° = -79.2 kJ/mol

Equation 2: C (s) + 2 F₂ (g) → CF₄ (g) ∆H° = 141.3 kJ/mol

Equation 3: 2 C(s) + 2 H₂ (g) → C₂H₄ (g) ∆H° = -97.6 kJ/mol

Because of the way formation reactions are defined, any chemical reaction can be written as a combination of formation reactions, some going forward and some going back.

<h3 /><h3>FIRST STEP</h3>

First, to obtain the enthalpy of the desired chemical reaction you need one mole of C₂H₄ (g) on reactant side and it is present in first equation. Since this equation has one mole of C₂H₄ (g) on the product side, it is necessary to locate it on the reactant side (invert it).

When an equation is inverted, the sign of ΔH° also changes.

<h3>SECOND STEP</h3>

Now, you need 2 moles of CF₄ (g) on the product side. The second equation has 1 mole of CF₄ (g) on the product side, so it is necessary to multiply it by 2 to obtain 2 moles of CF₄ (g).

Since enthalpy is an extensive property, that is, it depends on the amount of matter present, since the equation is multiply by 2, the variation of enthalpy also.

<h3>THIRD STEP</h3>

Finally, you need 4 moles of HF (g) on the product side. The first equation has 2 moles of HF (g) on the product side, so it is necessary to multiply it by 2 to obtain 4 moles of the compound.

Since the equation is multiply by 2, the variation of enthalpy also is multiplied by 2.

<h3>SUMMARY</h3>

In summary, you know that three equations with their corresponding enthalpies are:

Equation 1: 2 H₂ (g) + 2 F₂ (g) → 4 HF (g) ∆H° = -158.4 kJ/mol

Equation 2: 2 C (s) + 4 F₂ (g) → 2 CF₄ (g) ∆H° = 282.6 kJ/mol

Equation 3: C₂H₄ (g) → 2 C(s) + 2 H₂ (g) ∆H° = 97.6 kJ/mol

Adding or canceling the reactants and products as appropriate, and adding the enthalpies algebraically, you obtain:

C₂H₄ (g) + 6 F₂ (g) → 2 CF₄ (g) + 4 HF (g) ΔH°= 221.8 kJ/mol

Finally, the enthalpy change for the reaction is 221.8 kJ/mol.

Learn more about molar enthalpy:

7 0

2 years ago

Complete the sentence using ide, ate or Ic. To determine the name of an anion, you take the name of its element and replace the

lara31 [8.8K]

To determine the name of an anion, you take the name of its element and replace the end with "ide".

<h3>What is an anion?</h3>

An anion in chemistry is a negatively charged ion.

Anions are usually formed when a non-metallic atom gains electron(s).

An anion is usually named by taking the elemental name, removing the ending, and adding “ide.

Examples of anions are as follows:

fluoride (F-)
Chloride (Cl-)
Iodide (I-)

Learn more about anions at: brainly.com/question/15578817

#SPJ1

8 0

2 years ago

A sample of an ideal gas has a volume of 2.21 L at 282 K and 1.03 atm. Calculate the pressure when the volume is 1.84 L

PIT_PIT [208]

Answer:

1.33 atm

Explanation:

use general gas equation P1 V1/ T1 = P2 V2/ T2

rearrange and make P2 the subject then solve,it should give you 1.33 atm

3 0

3 years ago

Two liquids, a and b are immiscible. liquid a has a density of 0.89 g/ml. liquid b has a density of 0.72 g/ml. what would you ex

Burka [1]

In the given above, we have two densities which are 0.89 g/mL and 0.72 g/mL. We are also given that the liquids are immiscible. After the settlement of the liquids, they will form two layers.

The heavier substance, the one which has a higher density will be at the bottom and the lighter substance, the one which has a lower density will be at the top layer.

5 0

4 years ago

The purpose of this guide is to help you write a clear and concise report that summarizes the lab I just completed. This lab sho

Masja [62]

Answer:

The purpose of this guide is to help you write a clear and concise report that summarizes the lab I just completed. This lab showed me how water carries rocks to a new location. For instance how the first model showed how a stream would act with light drizzle to downpour as I saw the outcomes were all if not completely then partially different

I read the information that was given to me before I started each lab lesson and went on from there.

Explanation:

:)

3 0

2 years ago

Read 2 more answers

Calculate the [H+] for (a) black coffee with a pH of 3.59