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2 years ago

Select the correct statements below.

Chemistry

1 answer:

ASHA 777 [7]2 years ago

8 0

Answer: The correct answer is Option b.

Explanation:

Effective nuclear charge is defined as the attraction of the protons present in the nucleus of an atom to the outermost electrons.

Trend across a period:

On moving across the period, successive electrons gets add up to the orbitals in the same shell and the shielding of the nuclear charge by the core electrons do not change to a large extent so as to decrease the attraction of electrons to the nucleus. This results in the increase of effective nuclear charge.

Trend down the group:

On moving down the group, the outermost electron gets further away from the nucleus. The shielding effect by the core electrons get increased. This result in the decrease of effective nuclear charge. As, the principal quantum number increases, the effective nuclear charge gets decreased and screening effect increases.

Atomic radius of an atom is defined as the total distance from the nucleus to the outermost shell of the atom.

Trend down the group:

On moving down the group, new shell gets add up around the nucleus of an atom and the outermost shell gets far. The distance between the nucleus and outermost shell increases. This results in the increase of atomic radii of the atom.

Trend across a period:

On moving across a period, more and more electrons get add up in the same shell. The attraction between the last electron and nucleus increases, which results in the shrinkage of size of an atom. So, the atomic radii gets decreased.

For the given options:

Option a: Chlorine atom is smaller than sulfur atom because of the increase in the attraction of electrons by the nucleus.

Option b: Oxygen atom is smaller than Carbon atom because of the increase in effective nuclear charge in the atom.

Option c: Potassium atom is smaller than rubidium atom because of the addition of new shell around rubidium atom and also potassium has more effective nuclear charge as compared to rubidium.

Option d: Sodium atom is larger than magnesium atom because of less effective nuclear charge in sodium.

Hence, the correct answer is Option b.

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Two substances in a mixture differ in density and particle size. These properties can be used to

lianna [129]

Answer:

(1) separate the substances

(2) chemically combine the substances

(3) determine the freezing point of the mixture

(4) predict the electrical conductivity of the mixture

Explanation:

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2 years ago

A precipitate of zinc hydroxide can be formed using the reaction below.

worty [1.4K]

Answer:

Option B is correct. KOH is the limiting reagent, and 0.27 mole of Zn(OH)2 precipitate is produced.

Explanation:

Step 1: Data given

Number of moles ZnCl2 = 0.36 moles

Number of moles KOH = 0.54 moles

Step 2: The balanced equations

ZnCl2(aq) + 2 KOH(aq) → Zn(OH)2(s) + 2 KCl(aq)

For 1 mol ZnCl2 we need 2 moles KOH to produce 1 mol Zn(OH)2 and 2 moles KCl

Step 3: Calculate the limiting reactant.

KOH is the limiting reactant. It will completely be consumed (0.54 moles). ZnCl2 is in excess. There will react 0.54/2 = 0.27 moles

There will remain 0.36 - 0.27 = 0.09 moles.

Step 4: The products

There will be produced 2 moles KCl and 1 mol Zn(OH)2. Zn(OH)2 is the precipitate produced.

For 1 mol ZnCl2 we need 2 moles KOH to produce 1 mol Zn(OH)2 and 2 moles KCl

For 0.54 moles KOH, we will produce 0.27 moles precipitate (Zn(OH)2)

Option A is not correct because 0.27 mol of Zn(OH)2 will precipitate, not 0.54 mol

Option B is correct

Option C is not correct because ZnCl2 is not the limiting reactant, but the excess reactant

Option D is not correct because ZnCl2 is not the limiting reactant, but the excess reactant

7 0

2 years ago

The complex ion, [ni(nh3)6] 2+, has a maximum absorption near 580 nm. calculate the crystal field splitting energy (in kj/mol) f

Wewaii [24]

In given data:
maximum absorption wavelength λ = 580 nm = 580 x 10⁻⁹ m
write the equation to find the crystal field splitting energy:
E = hC / λ
Here, E is the crystal field splitting energy, h = 6.63 x 10⁻³⁴ J.sec is Planck's constant and C = 3 x 10⁸ m/sec is speed of light.
substitute in the equation above:
E = (6.64 x 10⁻³⁴ x 3 x 10⁸) / (580 x 10⁻⁹) = 3.43 x 10⁻¹⁹J
This crystal field splitting energy is for 1 ion.
Number of atoms in one mole, NA = 6.023 x 10²³
to calculate the crystal field splitting energy for one mole:
E(total) = E x NA
= (3.43 x 10⁻¹⁹) x (6.023 x 10²³) = 206 kJ/ mole

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2 years ago

Complete the equation for the dissociation of cdcl2(aq). omit water from the equation because it is understood to be present.

mixas84 [53]

Cadmium chloride is a highly soluble compound. The equation for its dissolution is:

CdCl₂(s) → Cd⁺²(aq) + 2Cl⁻(aq)

This dissociation in water allows for the cadmium and chlorine ions to take part in reactions. This is the reason that solutions of chemicals are prepared when a reaction needs to take place.

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2 years ago

14. What is the pH of a 0.24 M solution of sodium propionate, NaC3H502, at 25°C? (For

Murrr4er [49]

Answer:

9.1

Explanation:

Step 1: Calculate the basic dissociation constant of propionate ion (Kb)

Sodium propionate is a strong electrolyte that dissociates according to the following equation.

NaC₃H₅O₂ ⇒ Na⁺ + C₃H₅O₂⁻

Propionate is the conjugate base of propionic acid according to the following equation.

C₃H₅O₂⁻ + H₂O ⇄ HC₃H₅O₂ + OH⁻

We can calculate Kb for propionate using the following expression.

Ka × Kb = Kw

Kb = Kw/Ka = 1.0 × 10⁻¹⁴/1.3 × 10⁻⁵ = 7.7 × 10⁻¹⁰

Step 2: Calculate the concentration of OH⁻

The concentration of the base (Cb) is 0.24 M. We can calculate [OH⁻] using the following expression.

[OH⁻] = √(Kb × Cb) = √(7.7 × 10⁻¹⁰ × 0.24) = 1.4 × 10⁻⁵ M

Step 3: Calculate the concentration of H⁺

We will use the following expression.

Kw = [H⁺] × [OH⁻]

[H⁺] = Kw/[OH⁻] = 1.0 × 10⁻¹⁴/1.4 × 10⁻⁵ = 7.1 × 10⁻¹⁰ M

Step 4: Calculate the pH of the solution

We will use the definition of pH.

pH = -log [H⁺] = -log 7.1 × 10⁻¹⁰ = 9.1

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2 years ago