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Amanda [17]
2 years ago
15

Which of the following is an example of a physical change? A) grinding coffee beans B) baking a cake C) converting water to hydr

ogen and oxygen D) digesting a cheeseburger E) burning coal
Chemistry
1 answer:
lara [203]2 years ago
5 0

Answer: A) grinding coffee beans

Explanation:

A physical change is defined as a change in which there is alteration in shape, size etc. No new substance gets formed in these reactions.

A chemical change is defined as a change in which a change in chemical composition takes place. A new substance is formed in these reactions.

1. Grinding coffee : Only change in size takes place, thus a physical change

2. Baking a cake: the chemical reaction occurs by combination of flour with oxygen , thus a chemical change.

3.:converting water to hydrogen and oxygen: The decomposition iof water takes place, thus is a chemical change

4.Burning of coal: the chemical reaction occurs by combination of carbon with oxygen , thus a chemical change.

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SeF6 1. Lewis Structure 2. Perspective drawing 3. Number of atoms bonded to central atom 4. Number of non-bonding electron pairs
Anarel [89]

The answer is- SF_{6} is octahedral in electronic and molecular geometry with 6 Fluorine atoms bonded to central atom S.

Lewis structures are the diagrams in which the valence electrons of the atoms of a compound are arranged around the atoms showing the bonding between the atom and the lone pair of electrons existing in the molecule.

Determine the molecular geometry of SF_{6}.

  • Valence Shell Electron Pair Repulsion theory is commonly known as VSEPR theory and it helps to predict the geometry of molecules.
  • According to this theory, electrons are arranged around the central atom of the molecule in such a way that there is minimum electrostatic repulsion between these electrons.
  • Now, calculate the total number of valence electrons in SF_{6}.

Valence\ electrons\ in\ SF_{6}= Valence\ electrons\ in\ S +\ 6(Valence\ electrons\ in\ F)

Valence electrons of S = 6

Valence electrons of F = 7

Thus, the valence electrons in SF_{6} are-

Valence\ number\ of\ electrons\ in\ SF_{6} = (6) + 6(7) = 48\ electrons.

  • The Lewis structure of SF_{6} is - (Image attached).
  • In the structure, the number of atoms bonded to central atom (S) = 6.
  • Number of non-bonding electron pairs on the central atom = 0 (as all the valence electrons are bonded to F).
  • Electronic geometry in case of 6 bond pairs is octahedral.
  • Molecular geometry us also octahedral with bond angles 90°.
  • Central atom is sp3d2 hybridised.
  • SF_{6} is a non-polar molecule.

To learn more about Lewis structures visit:

brainly.com/question/12307841?referrer=searchResults

#SPJ4

7 0
1 year ago
How are the following aspects of a reaction affected by the addition of a catalyst? 1) activation energy of the reverse reaction
snow_tiger [21]

These are four questions and four answers.

Answers:

1) activation energy of the reverse reaction

     b. Decreased

2) Rate of the forward reaction

    a. Increased

3) Rate of the reverse reaction

    a. Increased

4) Activation energy of the forward reaction

    b. decreased

Explanation:

<em>Activarion energy</em> is the energy required by the reactants to form the intermediate transition state and become products.

<em>Catalysts</em> are substances that change the path of the chemical reactions, lowering the activation energy, and thus speeding up the rate of the reactions, since the products can reach the new lower activation energy faster.

The equilibrium reactions are the chemical process in which two reactions, the <em>forward and the reverese reactions</em>, occur simultaneously and at the same rate.  The equlibrium reactions may be represented by:

  • A ⇄ B

Where A → B is the direct or forward reaction, and A ← B is the reverse reaction (note the inversed arrow, from right to left).

For the direct reaction A represents the reactants and B represents the products. On the other hand, B represents the reactants and A represents the reactants of the reverse reaction and A. This, is A is the reactant of the forward reaction and the product of the reverse reaction, while B is the reactant of the reverse reaction and the product of the forward reaction.

Since, <em>the addition of a catalyst</em> lowers the activation energy of the process, the new activation energy is lower for both the forward and the reverse reaction, meaning that:

1. <em>The activation energy of the reverse reaction is decreased</em> (option b. of the first question)

2.<em> The rate of the forward reaction is increased</em> (option a. of the second question)

3. <em>The rate of the reverse reaction is increased</em> (option a. of the third question).

4. <em>Activation energy of the forward reaction is decreased</em> (option b. of the fourth question).

In summary, the addition of a catalyst decreases the activation energy for both forward and reverse reactions, and increases the rate of both forward and reverse reactions.

3 0
3 years ago
Read 2 more answers
Outline two methods used by designers to assemble packages​
Lostsunrise [7]

Answer:

Product packaging design refers to the production of a product's exterior. Develop an organization. All these specifics allow one to consider what the sealed substance is about how to use it, who can use it, and maybe, What do you sell? For your product, there are several different packaging forms available.

Explanation:

8 0
2 years ago
Help :( i don’t understand
Natali [406]

Answer:

measuring cups, do you have them? look

4 0
2 years ago
Read 2 more answers
What is the molecule that senses heat stress in a cell?
nlexa [21]

Answer: -

sigma factor mRNA RpoH sigma H sigma 32

Explanation: -

It is the heat shock sigma factor which activates due to heat. The factor will bind with to the polymerase-core-enzyme. After this other heat ans shock proteins are expressed.

This thus enable the cell to survive higher temperatures. Some of the enzymes that are expressed upon activation are chaperones, proteases and DNA-repair enzymes

8 0
3 years ago
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