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3 years ago

The highly reactive elements in group 7A are known for forming salts. What are they called?

2 answers:

7 0

Because the elements in group 7A are good at forming salts, the are called HALOGENS; the word 'halogen' mean SALT FORMERS. The halogens refers to the five non metallic elements that are found in group 7A, these are chlorine, bromine, iodine, fluorine and astatine. Each of these elements has seven electrons in their outermost shell and will readily react with metals to form ionic compounds. They all have oxidation number of -1.

iVinArrow [24]3 years ago

6 0

They are called halogens

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The destruction of the ozone layer by chlorofluorocarbons (CFC’s) can be described by the following reactions:ClO(g) + O3(g) ? C

tino4ka555 [31]

Answer:

ΔH°rxn = 54.08 kJ

Explanation:

Let's consider the following equations.

a) ClO(g) + O₃(g) ⇄ Cl(g) + 2 O₂(g) ΔH°rxn = –29.90 kJ

b) 2 O₃(g) ⇄ 3 O₂(g) ΔH°rxn = 24.18 kJ

We have to determine the value of heat of reaction for the following reaction: Cl(g) + O₃(g) ⇄ ClO(g) + O₂(g)

According to Hess's law, the enthalpy change in a chemical reaction is the same whether the reaction takes place in one or in several steps. That means that we can find the enthalpy of a reaction by adding the corresponding steps and adding their enthalpies. According to Lavoisier-Laplace's law, if we reverse a reaction, we also have to reverse the sign of its enthalpy.

Let's reverse equation a) and add it to equation b).

-a) Cl(g) + 2 O₂(g) ⇄ ClO(g) + O₃(g) ΔH°rxn = 29.90 kJ

b) 2 O₃(g) ⇄ 3 O₂(g) ΔH°rxn = 24.18 kJ

-------------------------------------------------------------------------------------------------

Cl(g) + 2 O₂(g) + 2 O₃(g) ⇄ ClO(g) + O₃(g) + 3 O₂(g)

Cl(g) + O₃(g) ⇄ ClO(g) +O₂(g)

ΔH°rxn = 29.90 kJ + 24.18 kJ = 54.08 kJ

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3 years ago

How are sex chromosomes different from other chromosomes

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Somatic Chromosomes are Diploid (2n)

Sex Chromosomes are Haploid (n)

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3 years ago

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Lymph nodes.
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3 years ago

Classify the possible combinations of signs for a reaction's ΔH and ΔS values by the resulting spontaneity

FinnZ [79.3K]

Answer :

(A) ΔH is positive and ΔS is negative → (2) Spontaneous in reverse at all temperatures

(B) ΔH is positive and ΔS is positive → (3) Spontaneous as written above a certain temperature

(C) ΔH is negative and ΔS is positive → (1) Spontaneous as written at all temperatures

(D) ΔH negative and ΔS is negative → (4) Spontaneous as written below a certain temperature

Explanation :

According to Gibb's equation:

$\Delta G=\Delta H-T\Delta S$

$\Delta G$ = Gibbs free energy

$\Delta H$ = enthalpy change

$\Delta S$ = entropy change

T = temperature in Kelvin

As we know that:

$\Delta G$ = +ve, reaction is non spontaneous

$\Delta G$ = -ve, reaction is spontaneous

$\Delta G$ = 0, reaction is in equilibrium

(A) ΔH is positive and ΔS is negative.

$\Delta G=\Delta H-T\Delta S$

$\Delta G=(+ve)-T(-ve)$

$\Delta G=(+ve)$

The reaction is non-spontaneous at all temperatures or spontaneous in reverse at all temperatures.

(B) ΔH is positive and ΔS is positive.

$\Delta G=\Delta H-T\Delta S$

$\Delta G=(+ve)-T(+ve)$

$\Delta G=(+ve)$ (at low temperature) (non-spontaneous)

$\Delta G=(-ve)$ (at high temperature) (spontaneous)

The reaction is spontaneous as written above a certain temperature.

(C) ΔH is negative and ΔS is positive.

$\Delta G=\Delta H-T\Delta S$

$\Delta G=(-ve)-T(+ve)$

$\Delta G=(-ve)$

The reaction is spontaneous as written at all temperatures

(D) ΔH is negative and ΔS is negative.

$\Delta G=\Delta H-T\Delta S$

$\Delta G=(-ve)-T(-ve)$

$\Delta G=(+ve)$ (at high temperature) (non-spontaneous)

$\Delta G=(-ve)$ (at low temperature) (spontaneous)

The reaction is spontaneous as written below a certain temperature.

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Eva8 [605]

Answer:

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