CHEMISTRY HIGH SCHOOL

Which phrase most accurately describes a chemical change?Question 3 options:

A change on the molecular level.


A change in appearance.


A change in taste.


A change in form.

Answers

Answer 1
Answer:

The phrase that most accurately describes a chemical change is; "A change on the molecular level."

The major difference between a physical change and a chemical change is that a chemical change involves a change in the composition of a substance.

This implies that the atoms in a substance are rearranged during a chemical change.

This rearrangement of atoms corresponds to change on a molecular level.

Learn more; brainly.com/question/6284546
Answer 2
Answer: The signs of a chemical reaction include
Production of a gas (bubbles)
Production of heat
Production of light
Color change
Production of a solid (precipitate) in a solution

So from those answers we see that A is the correct answer.

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Answers

Answer:

1. is B 2. is C or B

Explanation:

Your boss asks you to design a room that can be as soundproof as possible and provides you with threesamples of material. The only information on each sample's label is the material's coefficient of absorption.
The coefficient of absorption listed on Sample A is 30%, on Sample B is 47%, and on Sample C is 62%.
When your boss asks for your choice and the reasoning behind it, what would you tell him?
A. Sample A would be best, because the percentage of the energy in an incident wave that remains in a reflected wave from this
material is the smallest.
B. Sample C would be best, because the percentage of the energy in an incident wave that remains in a reflected wave from this
material is the smallest.
C. Sample C would be best, because the percentage of the energy in an incident wave that remains in a reflected wave from this
material is the largest.
D. Sample A would be best, because the percentage of the energy in an incident wave that remains in a reflected wave from this
material is the largest.

Answers

Answer: The correct answer is Option C.

Explanation: For a room to be soundproof, there should be minimum reflection of the sound waves and maximum absorption of the waves.

According to the question, the coefficient of absorption is maximum for Sample C. So, this sample will reflect minimum waves and will absorb maximum waves.

Hence, this sample is the best for making the room soundproof. Hence, the correct answer is Option C.
The right answer for the question that is being asked and shown above is that: "B. Sample C would be best, because the percentage of the energy in an incident wave that remains in a reflected wave from this material is the smallest."

Which balanced equation represents a redoxreaction?
(1) CuCO3(s) ==> CuO(s) + CO2(g)
(2) 2KClO3(s)==>2KCl(s) + 3O2(g)
(3) AgNO3(aq) + KCl(aq) ==>AgCl(s) + KNO3(aq)
(4) H2SO4(aq) + 2KOH(aq)==> K2SO4(aq) + 2H2O(l)

Answers

Option no. 2  Balanced equation     

2KClO3(s)⇒2KCl(s) + 3O2(g)
      K=2             K=2
      Cl=2            Cl=2
      O=6             O=6

Given the redox reaction:Cr3+ + Al-->Cr + Al3+
As the reaction takes place, there is a transfer of
(1) electrons from Al to Cr3+
(2) electrons from Cr3+ to Al
(3) protons from Al to Cr3+
(4) protons from Cr3+ to Al

Answers

Answer: (1) electrons from Al to Cr^(3+)

Explanation: Oxidation-reduction reaction or redox reaction is defined as the reaction in which oxidation and reduction reactions occur simultaneously.

Oxidation reaction is defined as the reaction in which a substance looses its electrons. The oxidation state of the substance increases.

Reduction reaction is defined as the reaction in which a substance gains electrons. The oxidation state of the substance gets reduced.

For the given reaction:

Cr^(3+)+Al\rightarrow Cr+Al^(3+)

The oxidation state of chromium reduces from +3 to 0, it is getting reduced and gains electrons. The oxidation state of aluminium increases from 0 to +3. Thus, it is getting oxidized and it loses electrons. Thus electrons are transferred from Al to Cr^(3+)
In this reaction, Al lose electrons and change to Al3+. Cr3+ gain electrons and change to Cr. So the electrons transfer from Al to Cr3+. Protons will not transfer in a chemical reaction. So the answer is (1).

Which of these processes indicates that smelting copper is a chemical changea)it involves melting copper to form liquid metal
b)it involves heating charcoal to high tempuratures
c)it involves drawing copper into long wires
d)it involves breaking molecular bonds between copper compounds

Answers

The correct answer is D:


it involves breaking molecular bonds between copper compounds .


The explanation :


-when we melt a copper it is a physical change because the substance is still copper and have the same shape.


- but for example Burning a copper it is a chemical change. Fire activates a chemical reaction between copper and oxygen.


-The oxygen in the air reacts with the copper and the chemical bonds are broken.


- the chemical change is changing the other compound bonded to the copper atoms.


So, the correct answer is D
Answer is d. The material can be phsycal changes into a differnt shape or state (gas, liquid, solid) and its will still be essentially copper. A chemical change is changing what other elements or compound is bonded to the copper atoms

A catalyst is _____.-Choices-
not used up in a reaction
the product of a combustion reaction
one of the reactants in a single-replacement reaction
a solid product of a reaction

Answers

Answer: Option (a) is the correct answer.

Explanation:

A catalyst is the substance which helps in increasing the rate of a reaction without itself getting consumed in the reaction.

A catalyst changes the path of reaction so that molecules with lower energy can easily participate in the reaction. As a result, formation of products increases.

Thus, we can conclude that out of the given options, a catalyst is not used up in a reaction.
A catalyst isn't used up in the reaction. It is only used to speed up the process of the reaction, but it isn't used up to form any new compounds
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