CHEMISTRY HIGH SCHOOL

Which physical change is endothermic?(1) CO2(s)-->CO2(g) (3) CO2(g)-->CO2(l)
(2) CO2(l)-->CO2(s) (4) CO2(g)-->CO2(s)

Answers

Answer 1
Answer:

Answer: The correct option is 1.

Explanation:Endothermic reactions are the reactions in which heat is provided to break down the reactant molecules.

In option 1:

The stronger intermolecular forces between the particles in solid molecule are broken down to convert into gaseous form. Hence, some energy in the form of heat is provided to move them far apart. Therefore, it is considered as an endothermic reaction.

In option 2, 3 and 4:

All the other processes involves the formation of bonds and thus there is no need to provide any energy.
Answer 2
Answer:

The physical change that is endothermic is \boxed{\left( 1 \right){\text{ C}}{{\text{O}}_{\text{2}}}\left( s \right) \to {\text{C}}{{\text{O}}_{\text{2}}}\left( g \right)}.

Further explanation:

Changes are of two types:

(A) Physical changes:

It is the process in which the physical properties of the system are affected. These changes can also be reversed by physical methods. In these kinds of changes, the molecular composition of the substance remains the same. These are reversible in nature and no new substances are formed. For example, boiling of water, chopping of wood, melting of wax are physical changes.

(B) Chemical changes:

In this change, new substances are formed by the chemical combination of the previous substances. The chemical properties of substance changes when it undergoes a chemical change. These are irreversible in nature. For example, fermentation of grapes, burning of wood, rusting of iron are chemical changes.

Endothermic reactions are those in which more energy needs to be supplied to the system than that released by it.

Exothermic reactions are those in which more energy is released by the system than that supplied to it.

(1){\text{C}}{{\text{O}}_{\text{2}}}\left( s \right) \to {\text{C}}{{\text{O}}_{\text{2}}}\left( g \right)

In this reaction, solid carbon dioxide is converted into gaseous carbon dioxide. The strong intermolecular force of attraction in solid needs to be broken down and energy is supplied for this purpose. Hence this is an endothermic process.

(2){\text{C}}{{\text{O}}_{\text{2}}}\left( l \right) \to {\text{C}}{{\text{O}}_{\text{2}}}\left( s \right)

In this reaction, liquid carbon dioxide is converted into solid carbon dioxide. The intermolecular forces in liquid molecules are weaker than that present in solid molecules and are broken down easily so energy is released during the process. Hence this is an exothermic process.

(3){\text{C}}{{\text{O}}_{\text{2}}}\left( g \right) \to {\text{C}}{{\text{O}}_{\text{2}}}\left( l \right)

In this reaction, gaseous carbon dioxide is converted into liquid carbon dioxide. The intermolecular forces in gas molecules are weaker than that present in liquid molecules and are broken down easily so energy is released during the process. Hence this is an exothermic process.

(4){\text{C}}{{\text{O}}_{\text{2}}}\left( g \right) \to {\text{C}}{{\text{O}}_{\text{2}}}\left( s \right)

In this reaction, gaseous carbon dioxide is converted into solid carbon dioxide. The intermolecular forces in gas molecules are weaker than that present in solid molecules and are broken down easily so energy is released during the process. Hence this is an exothermic process.

Learn more:

1. Which of these is an extensive property? brainly.com/question/1398514

2. Which of the phase changes is an exothermic change? brainly.com/question/1875234

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Physical and chemical changes

Keywords: physical change, chemical change, CO2, endothermic, exothermic, solid, liquid, gaseous, intermolecular forces, strong, weaker.

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The formation of an ionic bond involves (1 point)transfer of electrons. transfer of neutrons. transfer of protons. sharing of electrons.

Answers

By definition, an ionic bond involves the transfer of electrons. The resulting charged particles are then electrostatically attracted to one another, which is what forms the bond. 

Transfer of neutrons and protons never takes place in a chemical reaction (you have to talk about nuclear reactions instead), and the sharing of electrons takes place in a covalent bond.

Answer = Transfer of electrons.

The formation of an ionic bond involves \boxed{{\text{transfer of electrons}}}.

Further Explanation:

Chemical bond is termed as the attractive force that is present between various atoms, ions or molecules. The existence of different chemical compounds is a result of chemical bonds. These bonds can be formed by electron transfer or electron sharing. Protons and neutrons never participate in the bond formation.

Covalent bond

The mutual sharing of electrons between the bonded atoms results in the formation of covalent bonds. Covalent compounds are formed due to presence of these bonds. This type of bonding usually takes place between two or more non-metals.

Ionic bond

The interaction between a metal and a non-metal is defined as an ionic bond. It occurs via the formation of ions by the respective neutral atoms. Here the electrons are completely transferred from metals to non-metals. Metals form cations by the loss of electrons while non-metals form anions by the gain of electrons.

Ionic compounds exist as a result of ionic bonds are called ionic compounds. These compounds are hard solids, good conductors of heat and electricity, have high heat of fusion and high boiling and melting points.

Therefore the formation of ionic bond involves the transfer of electrons.

Learn more:

  1. Identification of ionic bonding: brainly.com/question/1603987
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Answer details:

Grade: High School

Subject: Chemistry

Chapter: Ionic and covalent compounds

Keywords: chemical bond, ionic bond, cation, anion, ionic compounds, transfer, electrons, protons, neutrons, chemical compounds.

The amount by which a machine multiplies an effort force is called ____.a. efficiency factor
b. fulcrum
c. mechanical advantage
d. resistance force

Answers

c. mechanical advantage 

Answer:

Mechanical Advantage

Explanation:

Write a nuclear equation for the fusion of two h−2 atoms to form he−3 and one neutron.

Answers

'Heavy' hydrogen (the isotope deuterium) , 2/1H is involved ,

[2= mass number, 1= atomic (proton) number]

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Determine the number of moles 28.8 g Br2

Answers

well, you would just divide 28.8 by the molar mass of Br2 (the gram amount on the periodic table x2 because there's two of them)

Which of the following is not an acid? HCl

H2SO4

HNO3

NaOH

Answers

NaOH is not an acid. It is categorized as a base, specifically a strong base, since it has the capability to accept protons from any proton donor and, when it is in aqueous form, it fully dissociates into ions of sodium and hydroxide. 

Any substance that tastes unpleasant in water solution, turns blue litmus paper red, reacts with some metals to release hydrogen, combines with bases to create salts, and stimulates chemical processes is considered an acid. Here among the given options, NaOH is a base. The correct option is D.

Any hydrogen-containing material that has the ability to donate a proton (hydrogen ion) to another chemical is considered an acid. A base is a molecule or ion that can take up an acid's hydrogen ion. Typically, sour tastes help to identify acidic chemicals.

An acid is not NaOH. It is categorized as a base, more specifically a strong base, because it can receive protons from any proton donor and completely dissociates into sodium and hydroxide ions in an aqueous form.

Thus the correct option is D.

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Which of the following is not a phase change?melting of snow
evaporation of water from the ocean
condensation of water vapor to form clouds
hydrogen and oxygen gas combining to form water vapor

Answers

Answer : The correct option is hydrogen and oxygen gas combining to form water vapor.

Explanation :

Phase change : It is a change from one state to another state without changes in chemical composition.

Phase change such as solid to liquid, liquid to vapor, vapor to liquid, liquid to solid, vapor to solid, solid to vapor.

  • Melting of snow is a fusion process in which phase changes from solid to liquid.
  • Evaporation of water from the ocean is a evaporation process in which phase changes from liquid to vapor.
  • Condensation of water vapor to form clouds  is condensation process in which phase changes from vapor to liquid.
  • Hydrogen and oxygen gas combining to form water vapor, there is no phase change in this reaction because a gas combine with another gas to form a water vapor as a gas.
hydrogen and oxygen gas combining to form water vapor is the correct answer.
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