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True [87]
3 years ago
6

Hen an electric current passes through liquid water, hydrogen gas passes accumulates at one electrode and oxygen accumulates at

the other. Which of the following is true?
A) A physical change has occurred, with energy is being absorbed.

B) A chemical change has occurred, with energy being given off.

C) A physical change has occurred, with energy being given off.

D) A chemical change has occurred, with energy being absorbed.
Chemistry
2 answers:
Step2247 [10]3 years ago
7 0
The correct option is D.
The reaction above is called dissociation of water, that is, water is broken down into oxygen and hydrogen through the passage of electric current. This is an example of a chemical reaction. The reaction is an endothermic reaction because energy is absorbed.
KATRIN_1 [288]3 years ago
7 0

Answer:The correct answer is option D.

Explanation:

Physical change : It is defined as change in shape, state or size of the substance. There is no change in composition of the substance and no new substance is formed.

Chemical change : it is defined as change in chemical composition of the substance. During this change formation of new substance takes place.

Decomposition of water can be written as:

H_2O(l)\overset{Electricity}\rightarrow H_2(g)+O_2(g)

In above decomposition reaction, energy is provided to the water molecule to break down into its constituent elements that is oxygen and hydrogen. Energy given to the molecule is in the form electrical energy.

Hence, yes it is a chemical change.

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Answer:

Reaction 5: Decomposition reaction.

Reaction 6: Single replacement reaction

Reaction 7: Combination reaction.

Reaction 8: Combustion reaction.

Explanation:

<u><em>Reaction 5:</em></u>    2KClO₃ → 2KCl + 3O₂.

  • It is a decomposition reaction.
  • A decomposition reaction is a type of chemical reaction in which a single compound breaks down into two or more elements or new compounds.
  • In this reaction: potassium chlorate decomposes into two single components (potassium chloride and oxygen).
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<u><em>Reaction 6:</em></u> Zn + 2HCl → H₂ + ZnCl₂.

  • It is a single replacement reaction.
  • A single-replacement reaction, a single-displacement reaction, is a reaction by which one (or more) element(s) replaces an/other element(s) in a compound.
  • It is most often occur if element is more reactive than the other, thus giving a more stable product.
  • In this reaction, zinc metal (more active) displaces the hydrogen to form hydrogen gas and zinc chloride, a salt. Zinc reacts quickly with the acid to form bubbles of hydrogen.

<u><em>Reaction 7:</em></u> N₂O₅ + H₂O → 2HNO₃.

  • It is a combination "synthesis" reaction.
  • A synthesis reaction has two or more reactants and only one product.
  • In this reaction, dinitrogen pentoxide reacts with water to produce nitric acid.
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<u><em>Reaction 8:</em></u> 2C₂H₆ + 7O₂ →  4CO₂ + 6H₂O.

  • It is a combustion reaction.
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Electronegativity is the strength an atom has to attract a bonding pair of electrons to itself. When a chlorine atom covalently bonds to another chlorine atom, the shared electron pair is shared equally. The electron density that comprises the covalent bond is located halfway between the two atoms.

But what happens when the two atoms involved in a bond aren’t the same? The two positively charged nuclei have different attractive forces; they “pull” on the electron pair to different degrees. The end result is that the electron pair is shifted toward one atom.

ATTRACTING ELECTRONS: ELECTRONEGATIVITIES

The larger the value of the electronegativity, the greater the atom’s strength to attract a bonding pair of electrons. The following figure shows the electronegativity values of the various elements below each element symbol on the periodic table. With a few exceptions, the electronegativities increase, from left to right, in a period, and decrease, from top to bottom, in a family.

Electronegativities give information about what will happen to the bonding pair of electrons when two atoms bond. A bond in which the electron pair is equally shared is called a nonpolar covalent bond. You have a nonpolar covalent bond anytime the two atoms involved in the bond are the same or anytime the difference in the electronegativities of the atoms involved in the bond is very small.



Now consider hydrogen chloride (HCl). Hydrogen has an electronegativity of 2.1, and chlorine has an electronegativity of 3.0. The electron pair that is bonding HCl together shifts toward the chlorine atom because it has a larger electronegativity value.

A bond in which the electron pair is shifted toward one atom is called a polar covalent bond. The atom that more strongly attracts the bonding electron pair is slightly more negative, while the other atom is slightly more positive. The larger the difference in the electronegativities, the more negative and positive the atoms become.

Now look at a case in which the two atoms have extremely different electronegativities — sodium chloride (NaCl). Sodium chloride is ionically bonded. An electron has transferred from sodium to chlorine. Sodium has an electronegativity of 1.0, and chlorine has an electronegativity of 3.0.

That’s an electronegativity difference of 2.0 (3.0 – 1.0), making the bond between the two atoms very, very polar. In fact, the electronegativity difference provides another way of predicting the kind of bond that will form between two elements, as indicated in the following table.

Electronegativity DifferenceType of Bond Formed0.0 to 0.2nonpolar covalent0.3 to 1.4polar covalent> 1.5ionic

The presence of a polar covalent bond in a molecule can
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The answer regarding the transformation is addition and hydration.

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