How do you find empirical formula

Salicylic acid (C₇H₆O₃) reacts with acetic anhydride (C₄H₆O₃) to form acetylsalicylic acid (C₉H₈O₄).

lions [1.4K]

Answer:

The limiting reactant is the Salicylic acid (C₇H₆O₃)

Explanation:

In order to find the limting reactant or the excess reactant of a chemical reaction we have to compare the moles of each reactant to the stoichiometry of the reaction; we usually make rules of three.

First of all we need to convert the mass of the reactants, to moles:

70 g / 138 g/mol = 0.507 moles of salicylic acid

80g / 102 g/mol = 0.784 moles of acetic anhydride

The reaction is: 2C₇H₆O₃ (aq) + C₄H₆O₃(aq) → 2C₉H₈O₄(aq) + H₂O(l)

Ratio is 2:1.

2 moles of salicylic acid need 1 mol of acetic anhydride to react

Then, 0.507 moles of salicylic will react with (0.507 . 1) / 2 = 0.254 moles of acetic anhydride (It's ok, I have 0.784 moles and I only need 0.254 moles, so acetic anhydride still remains, the C₄H₆O₃ is the excess reactant)

In conclussion, the limiting reactant is the Salicylic acid (C₇H₆O₃)

Let's verify: 1 mol of anhyride needs 2 moles of salicylic acid

Therefore, 0.784 moles of anhydride will react with (0.784 . 2) /1 = 1.57 moles. → We do not have enough C₇H₆O₃, we have 0.507 moles but we need 1.57.

4 0

3 years ago

an electron in the 3rd shell of an Aluminium atom moves to the first shell in a bombardment process. Calculate the frequency of

Liula [17]

Following the quantic theory, the energy of a photon equals the radiation frequency multiplied by the universal constant. ν = 2.923x10¹⁵ Hz. E = 3.09x10¹⁵Hz.

<h3>What is quantum mechanic?</h3>

It is the branch of physics that studies objects and forces at a very low scale, at atoms, subatoms, and particles levels.

Quantum mechanics states that the elemental particles that constitute matter -electrons, neutrons, protons- have the properties of a wave and a particle.

It emerges from the quantic theory exposed by Max Planck (1922), in which he affirmed that light propagates in energy packages or photons.

He discovered the Universal Planck constant, h, used to calculate the energy of a photon.

He stated that the energy of a photon (E) equals the radiation frequency (ν) multiplied by the universal constant (h).

E = νh

In the exposed example, we need to calculate the energy required to change from the 3rd shell to the first shell.

To do it, we should know that the energy in a level (Eₙ) equals the energy associated to an electron in the most inferior energy level (E₁) divided by the square of the shell number (n²).

Eₙ = E₁ / n²

E₁ is a constant. We can express it in Joules or electroVolts

E₁ = -2.18x10⁻¹⁸ J
E₁ = -13.6 eV

So, let us calculate the energy at level 1 and 3

Eₙ = E₁ / n²

E₁ = -2.18x10⁻¹⁸ J / 1² = -2.18x10⁻¹⁸ J

E₁ = -13.6 eV / 1² = -13.6 eV

E₃ = -2.18x10⁻¹⁸ J / 3² = -2.18x10⁻¹⁸ J / 9 = - 2.42x10⁻¹⁹ J

E₃ = -13.6 eV / 3² = -13.6 eV / 9 = - 1.51 eV

The change of energy can be calculated in two ways,

Option 1

ΔE = E₁ - E₃ = 2.18x10⁻¹⁸ - 2.42x10⁻¹⁹ = 1.93x10⁻¹⁸J

ΔE = E₁ - E₃ = 13.6 - 1.51 = 12.09 eV

Option 2

ΔE = -2.18x10⁻¹⁸ J (1/nf² - 1/ni²)

ΔE =-13.6 eV (1/nf² - 1/ni²)

Where nf is the final level and ni is the initial level. When the electron passes from its initial level to its final level it is called electronic transition.

ni = 3
nf = 1

ΔE = -2.18x10⁻¹⁸ J (1/nf² - 1/ni²)

ΔE = -2.18x10⁻¹⁸ J (1/1² - 1/3²)

ΔE = -2.18x10⁻¹⁸ J (1 - 0.111)

ΔE = -2.18x10⁻¹⁸ J (0.888)

ΔE = - 1.937x10⁻¹⁸ J

or

ΔE = -13.6 eV (1/nf² - 1/ni²)

ΔE = -13.6 eV (1/1² - 1/3²)

ΔE = -13.6 eV (1 - 0.111)

ΔE = -13.6 eV (0.888)

ΔE = -12.08 eV

This is the energy required for the electron to go from n= 3 to n = 1. The negative sign (-) means energy (as light or photons) released or emitted.

If we want to express the result in Hz, we just need to make a conversion.

1Hz ⇔ 6.626x10⁻³⁴J ⇔ 4.136x10¹⁵ eV.

The energy required for the electron to go from n= 3 to n = 1 is 3.09x10¹⁵ Hz.

Now, we need to calculate the frequency, ν. This is, how many times the wave oscillates back and foward per second.

To do it, we will use the universal Planck constant, h, and the absolute value of the energy, E.

ν = E/h = 1.937x10⁻¹⁸ J / 6.626x10⁻³⁴ Js = 2.923x10¹⁵ 1/s = 2.923x10¹⁵ Hz.

Answer:

Frequency, ν = E/h = 2.923x10¹⁵ Hz.
Energy, E = 3.09x10¹⁵ Hz.

You can learn more about quantum mechanic at

brainly.com/question/11855107

brainly.com/question/23780112

brainly.com/question/11852353

5 0

2 years ago

-Which of the following best explains how human activities can directly contribute to landslides?

Alborosie

Humans disturb the earth and because of this, the earth is weakened

8 0

4 years ago

Given the propane molecule C3H8(g)! a) What is the balanced equation for the combustion of propane in O2?(20 pts.) b) What is th

lubasha [3.4K]

Answer:

The answer to your question is below

Explanation:

Propane = C₃H₈

Process

1.- Write the chemical reaction

C₃H₈ + O₂ ⇒ CO₂ + H₂O

balanced chemical reaction

C₃H₈ + 5O₂ ⇒ 3CO₂ + 4H₂O

Reactants Elements Products

3 C 3

8 H 8

10 O 10

b) Standard enthalpy

Propane -104.7 kJ/mol

Oxygen 0 kJ/mol

Carbon dioxide -393.5 kJ/mol

Water -241.8 kJ/mol

ΔH° = ∑ΔH° products - ∑H° reactants

ΔH° = 3(-393.5) + 4(-241.8) - [(-104.7) + 0]

-Simplification

ΔH° = -1180.5 kJ/mol - 967.2 kJ/mol + 104.7 kJ/mol

ΔH° = - 2042.5 kJ/mol

This reaction is exothermic because ΔH° is negative.

4 0

3 years ago

Consider the following comparison.

Vera_Pavlovna [14]

Answer:

C).

Explanation:

Because the organs in our body helps us to function.

5 0

3 years ago

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