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3 years ago

#1: The element that loses electrons in a chemical reaction is said to have been which of the following?

2 answers:

5 0

#1: The element that loses electrons in a chemical reaction is said to have been which of the following? A. reduced

B. oxidized

C. combusted

D. rusted

**idk, is it reduced or oxidized??

Answer: oxidized. The element that loses electrons increases its oxidation number (becomes more positve or less negative) and this is oxidation.

Which type of reaction occurs if one element gains electrons and another loses electrons?

A. combustion

B. synthesis

C. oxidation-reduction

D. double-displacement

**my answer: C

Yes, oxidation-reduction

#3: What is the oxidation number for phosphorus in H4P2O7?

A. +5

B. +3

C. +1

D. - 1

**my answer: A. +5

This is the way to calculate it 4(+1) + 2x + 7(-2) = 0 => x = +5

#4: What is the oxidation number for phosphorus in Na2HPO3?

A. +5

B. +3

C. +1

D. - 1

**my answer; B. +3

is that right??

Right

2(+1) + 1 + x + 3(-2) = 0 => x = 6 -1 -2 = 3 (positive)

Lana71 [14]3 years ago

4 0

Answer:

For 1: The correct option is B.

For 2: The correct option is C.

For 3: The correct option is A.

For 4: The correct option is B.

Explanation:

For 1:

There are two types of reaction based on the basis of exchange of electrons.

The reaction in which an element gain electrons is considered as reduction reaction and the species gets reduced in the reaction.

The reaction in which an element looses electrons is considered as oxidation reaction and the species gets oxidized in the reaction.

Hence, the element which looses electrons in a chemical reaction is said to have been oxidized. So, the correct option is B.

For 2:

Combustion reaction are the chemical reactions in which a hydrocarbon is decomposed to carbon dioxide and water in the presence of oxygen.

Synthesis reaction is the chemical reaction in which two or more compounds combine to form a larger molecule by releasing some by-products.

Oxidation-reduction reaction is the chemical reaction in which one element gains electrons and another element looses electrons. This reaction is known as redox reactions.

Double displacement reactions are the chemical reactions in which exchange of ions takes place.

Hence, the correct option is C.

For 3:

Oxidation number is the number given to an element in a chemical compound which represents the number of electrons lost or gained by that element.

Oxidation number of hydrogen = +1

Oxidation number of oxygen = -2

Oxidation number of phosphorous in $H_4P_2O_7$ is:

$4(+1)+2x+7(-2)=0\\\\x=+5$

Hence, the correct option is A.

For 4:

Oxidation number is the number given to an element in a chemical compound which represents the number of electrons lost or gained by that element.

Oxidation number of Sodium = +1

Oxidation number of oxygen = -2

Oxidation number of Hydrogen = +1

Oxidation number of phosphorous in $Na_2HPO_3$ is:

$2(+1)+1+x+3(-2)=0\\\\x=+3$

Hence, the correct option is B.

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

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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

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.

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2 years ago

Iron(iii) oxide is formed when iron combines with oxygen in the air. How many moles of Fe2O3 are formed when 55.8 g or Fe reacts

iogann1982 [59]

Answer: The correct answer is Option B.

Explanation:

To calculate the number of moles, we use the formula:

$Moles=\frac{\text{Given mass}}{\text{Molar mass}}$

Moles of Iron

Molar mass of iron = 55.8 g/mol

Given mass of iron = 558.8

Putting values in above equation, we get:

$Moles=\frac{55.8g}{55.8g/mol}=1mole$

For the given chemical equation:

$4Fe(s)+3O_2(g)\rightarrow 2Fe_2O_3(s)$

By Stoichiometry,

4 moles of Iron produces 2 moles of Iron(III) oxide

So, 1 mole of Ion will produce = $\frac{2}{4}\times 1$ = 0.5 mole of Iron (III) oxide.

Hence, the correct answer is Option B.

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3 years ago

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Single replacement or single displacement reactions

Explanation:

In a single replacement or displacement reaction, the activity series is useful in predicting whether the reaction will take place or not.

In this reaction type, one substance is replacing another.

C + DE → CD + E

The relative positions of the two elements in the activity series provides the driving force for the single replacement reaction.
An element high up in the series will displace one that is lower in the series because it is more reactive.

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False because a compound is one or more elements

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