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4 years ago

Silicon has a relatively large latent heat of vaporization of 12800 J/g. This indicates that silicon has:

Chemistry

2 answers:

Lesechka [4]4 years ago

7 0

strong attraction between liquid particles

Lera25 [3.4K]4 years ago

3 0

Explanation:

When without any change in temperature heat required for conversion of unit mass of a liquid into its vapor state is known as latent heat of vaporization.

When we say a molecule has large heat of vaporization then it means that the liquid or substance has strong intermolecular forces of attraction between its particles and to overcome those forces high heat needs to be provided.

Whereas low heat of vaporization means the intermolecular forces between particles of a liquid or substance can be overcome by slight or low heating of the substance.

Thus, we can conclude that when silicon has large latent heat of vaporization of 12800 J/g then this indicates that particles of silicon are held by strong intermolecular forces. Therefore, high heat is required to change silicon from liquid to vapor state.

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Using the equations

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

Problem PageQuestion The airbags that protect people in car crashes are inflated by the extremely rapid decomposition of sodium

Shalnov [3]

Answer:

1. 2NaN₃(s) → 2Na(s) + 3N₂(g)

2. 14.5 g NaN₃

Explanation:

The answer is incomplete, as it is missing the required values to solve the problem. An internet search shows me these values for this question. Keep in mind that if your values are different your result will be different as well, but the solving methodology won't change.

" The airbags that protect people in car crashes are inflated by the extremely rapid decomposition of sodium azide, which produces large volumes of nitrogen gas. 1. Write a balanced chemical equation, including physical state symbols, for the decomposition of solid sodium azide (NaN₃) into solid sodium and gaseous dinitrogen. 2. Suppose 71.0 L of dinitrogen gas are produced by this reaction, at a temperature of 16.0 °C and pressure of exactly 1 atm. Calculate the mass of sodium azide that must have reacted. Round your answer to 3 significant digits. "

1. The <u>reaction that takes place is</u>:

2NaN₃(s) → 2Na(s) + 3N₂(g)

2. We use PV=nRT to <u>calculate the moles of N₂ that were produced</u>.

P = 1 atm

V = 71.0 L

n = ?

T = 16.0 °C ⇒ 16.0 + 273.16 = 289.16 K

1 atm * 71.0 L = n * 0.082 atm·L·mol⁻¹·K⁻¹ * 289.16 K

n = 0.334 mol

Now we <u>convert N₂ moles to NaN₃ moles</u>:

0.334 mol N₂ * $\frac{2molNaN_{3}}{3molN_2}$ = 0.223 mol NaN₃

Finally we <u>convert NaN₃ moles to grams</u>, using its molar mass:

0.223 mol NaN₃ * 65 g/mol = 14.5 g NaN₃

6 0

4 years ago

There is 35 mg of sodium in a can of Coke. You determine it to be 28 mg. What is your percent error?

natali 33 [55]

Answer:

The answer is

Explanation:

The percentage error of a certain measurement can be found by using the formula

$P(\%) = \frac{error}{actual \: \: number} \times 100\% \\$

From the question

actual volume = 35 mg

error = 35 - 28 = 7

The percentage error is

$P(\%) = \frac{7}{35} \times 100 \\ = \frac{1}{5} \times 100 \\ = 20$

We have the final answer as

Hope this helps you

8 0

3 years ago

Read 2 more answers

Iron forms rust, expressed as Fe2O3.

Elina [12.6K]

Answer:

it's C. 159.70 g

Explanation:

hopefully that helps

3 0

3 years ago

What is the relation between work done height mass and acceleration due to gravity

Zanzabum

Explanation:

Potential energy is the the relationship between work done height mass and acceleration due to gravity, because of this some objects also experience kinetic energy due to the factors mentioned above

6 0

1 year ago