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4 years ago

Are pure substances chemically combined

Chemistry

1 answer:

dmitriy555 [2]4 years ago

4 0

Pure substances can or can not be chemically combined.

Pure substances can be either elements or compounds, but not mixture. Mixture are different substances mixing together without being chemically combined, such as air, which is a mixture of oxygen, carbon dioxide, water etc. Mixture can be separated by physical methods, like filtration or decantation.

Meanwhile, elements are the substances that cannot be further separated by any means. No matter physical or chemical methods. Examples of elements are oxygen, hydrogen, neon and all the other ones from the periodic table. Compounds are basically elements joining together, but they’re chemically combined which means their electrons (kind of subatomic particle) are either shared or given away. These elements can only be separated by chemical methods like electrolysis or heating.

Therefore, as long as the substance cannot be separated by physical methods, it can be considered as a pure substance. We can now conclude that pure substance can be (element) or can not be (compound) chemically combined.

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Given the following values for the change in enthalpy (deltaH) and entropy (deltaS), which of the following processes can occur

Shtirlitz [24]

Answer:

Option A and B

Explanation:

(a) DeltaH = -84 kj mol-2 (-20 kcal mol-1), DeltaS = +125j mol-2K-1)(+30 cal mol-1 K-1)

Delta G = Delta H – T * DS

Substituting the given values, we get –

Delta G = -84 -298 *(125/1000) = -121.25 KJ/mol

Delta G is negative hence the process is spontaneous and will not violate the second law of thermodynamics

(b) DeltaH = -84 kj mol-2 (-20 kcal mol-1), DeltaS = -125j mol-2K-1)(-30 cal mol-1 K-1)

Delta G =-84 -298 *(-125/1000) = -46.75 KJ/mol

Delta G is negative hence the process is spontaneous and will not violate the second law of thermodynamics

Delta G = 84 -298 *(125/1000) = +46.75 KJ/mol

Delta G is positive hence the process is non-spontaneous and will violate the second law of thermodynamics

(d) DeltaH = +84 kj mol-2 (+20 kcal mol-1), DeltaS = +125j mol-2K-1)(-30 cal mol-1 K-1)

Delta G = 84 -298 *(-125/1000) = + 121.25 KJ/mol

Delta G is positive hence the process is non-spontaneous and will violate the second law of thermodynamics

6 0

3 years ago

A d1 octahedral complex is found to absorb visible light, with the absorption maximum occurring at 503 nm. calculate the crystal

Nina [5.8K]

237.9 KJ/mol⁻¹ crystal-field splitting energy is found to absorb visible light.

<h3>What is crystal-field splitting energy?</h3>

The energy of the electron configuration in the ligand field less the energy of the electronic configuration in the isotropic field is known as the crystal field energy.

The core metal ion's d orbitals split into two groups with various energies in an octahedral complex. The energy of the electron transition, which is related to the wavelength of the emitted light, is equal to the energy of the crystal-field splitting.

Δ = E = ℎ c / λ

Where,

where ℎ is the Planck constant, 6.62*10⁻³⁴m²kg s⁻¹, and c is the speed of light, 3 x 10⁸m s⁻¹.

Δ = 6.62*10⁻³⁴m²kg s⁻¹ / 503 x 10⁻⁹

= 3.95 x 10⁻¹⁹

= 3.95 x 10⁻¹⁹

This value is the splitting energy per ion.

To convert it to J/mol, we should multiply it by Avogadro number, 6.022 x 10²³mol⁻¹

= 3.95 x 10⁻¹⁹ x 6.022 x 10²³mol⁻¹

= 237.9 KJ/mol⁻¹

Therefore, the crystal-field splitting energy i<u>s 237.9 KJ/mol⁻¹ .</u>

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Learn more about crystal-field splitting energy, Here:

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8 0

2 years ago

How many atoms are in 9.35 moles of lithium?

Fudgin [204]

Answer:

3.45 moles Li contains 2.08 × 10 (to the power of)24 atoms .

Explanation:

The relationship between atoms and moles is:

1 mole atoms =

6.022 × 10 (to the power of)23

atoms

In order to determine how many atoms occupy a given number of moles, multiply the given moles by

6.022 × 10 (to the power of)23

atoms/mole

In the case of 3.45 moles lithium (Li):

3.45 mol Li × 6.022 × 10 (to the power of)23 atoms Li/ 1 mol Li =

2.08 × 10 (to the power of)24

atoms Li rounded to three

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3 years ago

A car driving east along the freeway at 60 m/s hits some traffic and after 7 seconds is

Vladimir79 [104]

Do u know how to solve area

4 0

3 years ago

Which is the Net Ionic Equation for:

arlik [135]

Answer: $2Fe^{3+}(aq)+3Mg(s)\rightarrow 3Mg^{2+}(aq)+2Fe(s)$

Explanation:

Complete ionic equation : In complete ionic equation, all the substance that are strong electrolyte and are present in an aqueous state and represented in the form of ions.

Net ionic equation : In the net ionic equations, we do not not include the spectator ions in the equations.

Spectator ions : The ions present on reactant and product side which do not participate in a reactions. The same ions present on both the sides.

The complete balanced ionic equation will be:

$2Fe^{3+}(aq)+6Cl^-(aq)+3Mg(s)\rightarrow 3Mg^{2+}(aq)+6Cl^-(aq)+2Fe(s)$

In this equation, $Cl^-$ are the spectator ions.

By removing the spectator ions from the balanced ionic equation, we get the net ionic equation.

The net ionic equation will be:

$2Fe^{3+}(aq)+3Mg(s)\rightarrow 3Mg^{2+}(aq)+2Fe(s)$

3 0

3 years ago

Are pure substances chemically combined​

Are pure substances chemically combined