CHEMISTRY HIGH SCHOOL

Which balanced equation represents a chemical change?(1) H2O(l) + energy → H2O(g)
(2) 2H2O(l) + energy → 2H2(g) + O2(g)
(3) H2O(l) → H2O(s) + energy
(4) H2O(g) → H2O(l) + energy

Answers

Answer 1

Answer:

The answer is B because energy was added to 2H2O in order to produce a chemical change of 2H2 and 02 seperately.

Answer 2

Answer:

Final answer:

The balanced equation that represents a chemical change is 2H2O(l) + energy → 2H2(g) + O2(g).

Explanation:

The balanced equation that represents a chemical change is (2) 2H2O(l) + energy → 2H2(g) + O2(g). In this equation, we see the reactant, water (H2O), being converted into two separate products, hydrogen gas (H2) and oxygen gas (O2), with the addition of energy. This indicates a chemical change taking place where new substances are formed.

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Which is the formula for the functional group in an amine?

Answers

An 'amine' is an organic compound primarily composed of carbon(C), hydrogen(H) and nitrogen (N).

Ammonia is a molecule in which the N atom is attached to 3 H atoms, in addition there is a lone pair of electrons on the central N atom. Amines are essentially derivatives of ammonia where one of more H atoms have been replaced by an alkyl (R) or aryl(Ar) group

For example:

R-NH2 == primary amine

R2-NH == secondary amine

R3N == tertiary amine

The amine functional group is R-NH2, 2 or 3 hydrogen atoms have been replaced by organic groups R, forming primary amine, secondary amine and tertiary amine.

hope this helps!

How are gamma rays made? Also, how are they important?

Answers

How are they made-
Gamma rays are given off by stars, and by some radioactive substances.
They are extremely high frequency waves, and carry a large amount of energy.USES-Because Gamma rays can kill living cells, they are used to kill cancer cells without having to resort to difficult surgery.This is called "Radiotherapy", and works because healthy cells can repair themselves fairly well when damaged by gamma rays - but cancer cells can't. Getting the dose right is very important!There's also targeted radiotherapy, where a radioactive substance is used to kill cancer cells - but it's a substance that'll be taken up by a specific part of the body, so the rest of the body only gets a low dose. An example would be using radioactive iodine to treat cancer in the thyroid gland.

Gamma rays are generated by radioactive atoms and in nuclear explosions. gamma rays are used to kill cancerous cells which is why it is used in medicine.

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: 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.

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.

Hypobromite is used to purify contaminated water. what is the formula for hypobromite

Answers

Answer: The formula for hypobromite $BrO^-$ .

Explanation:

Hypobromite is also called as alkaline bromine water with molecular formula of $BrO^-$ . It is used as germicide and antiparasitic

It is prepared by reacting bromine gas and alkali at 20 °C .

$Br_2+2OH^-\rightarrow Br^-+BrO^-+H_2O$

Oxidizing action of hypobromite ions.

$OBr^-+2H^++e^-\rightarrow (1)/(2)Br_2+H_2O$

The formula for Hypobromite is BrO

Which of the questions would involve the investigation of kinetic energy?A. What material makes the strongest boat?

B. How does the color of a boat affect heat absorption?

C. Do boats float higher in salt or fresh water?

D. What is the effect of a boat’s shape on its speed?

Answers

Answer:

D. What is the effect of a boat’s shape on its speed?

Explanation:

Kinetic energy can be defined as the energy possessed by an object or body due to its motion. It is the amount of work required to accelerate an object or body with a specific mass from its point of initial rest to a final velocity.

Mathematically, kinetic energy (K.E) is equal to 1/2(mv²).

Hence, the question which would involve the investigation of kinetic energy is "what is the effect of a boat’s shape on its speed?" because speed is directly related to the motion of the boat. Generally, the shape of the hull of a boat has an effect on the speed of the boat.

Answer:

What is the effect of a boat’s shape on its speed?

The depictions of ionic compounds do not show distinct compound units but rather a collection of ions in the ratio given by the formula. Explain how the drawing of NaCl both illustrates that the compound exists as a large collection of ions and that the ratio of sodium ions to chloride ions is 1-to-1 as indicated by the formula NaCl.

Answers

Answer:

The ionic compound NaCl has a Face Centered Cubic unit cell

The site for atoms are Face, center and Edges corner.

Effective number of atoms

Na+

1centers + 12edges x $(1)/(4)$ = 4 Na+

Cl-

6face x $(1)/(2)$ + $(1)/(8)$ x8 corners = 4Cl-

This is just one unit cell effective atom, there are thousand's of such unit cells are combined to form one such structure of NaCl. The real formula of NaCl is Na4Cl4 but for simplicity we use empirical formula that is NaCl.

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