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3 years ago

Can anyone help me? it's chemistry

Chemistry

1 answer:

ivann1987 [24]3 years ago

8 0

There is no any questions???

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What experimental observations indicate a chemical change is taking place?

Anestetic [448]

A chemical change is characterized of the formation of new substances or a chemical reaction. There are a number of observations that we can see if this type of change happens. One would be the formation of gas bubbles, this indicates that one of the products is a gas. Another observation would be a formation of a precipitate in the solution, it would indicate that the new solid formed is not soluble in the solution. A permanent color change in the solution would also indicate a chemical change because it may be that the new substance that is formed has its own distinct color when in solution.

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3 years ago

Which of the following is not a form of energy?

Dafna1 [17]

The answer is pressure

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3 years ago

Read 2 more answers

Write the Ka expression for an aqueous solution of hydrofluoric acid: (Note that either the numerator or denominator may contain

damaskus [11]

Answer:

Ka = ( [H₃O⁺] . [F⁻] ) / [HF]

Explanation:

HF is a weak acid which in water, keeps this equilibrium

HF (aq) + H₂O (l) ⇄ H₃O⁺ (aq) + F⁻ (aq) Ka

2H₂O (l) ⇄ H₃O⁺ (l) + OH⁻ (aq) Kw

HF is the weak acid

F⁻ is the conjugate stron base

Let's make the expression for K

K = ( [H₃O⁺] . [F⁻] ) / [HF] . [H₂O]

K . [H₂O] = ( [H₃O⁺] . [F⁻] ) / [HF]

K . [H₂O] = Ka

Ka, the acid dissociation constant, includes Kwater.

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2 years ago

A variation of the acetamidomalonate synthesis can be used to synthesize serine. The process involves the following steps: Ethox

Alex73 [517]

Answer:

See detailed mechanism in the image attached

Explanation:

The mechanism shown in detail below is the synthesis of serine in steps.

The first step is the attack of the ethoxide ion base on the diethyl acetamidomalonate substrate giving the enolate and formaldehyde.

The second step is the protonation of the oxyanion from (1) above to form an alcohol as shown.

Acid hydrolysis of the alcohol formed in (3) above yields a tetrahedral intermediate, a dicarboxyamino alcohol.

Decarboxylation of this dicarboxyamino alcohol yields serine, the final product as shown in the image attached.

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3 years ago

Cycloheptatrienone is stable, but cyclopentadienone is so reactive that it can't be isolated. Taking into account the polarity o

Lorico [155]

Answer and Explanation:

The resonance contributor in cyclopentadienone (as shown in the attachment below) results into the compound having a positive charge on the carbonyl group, C=O which accounts for a highly reactive anti-aromatic 4π system. And this illustrates the reason for its instability.

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3 years ago

Can anyone help me? it's chemistry​

Can anyone help me? it's chemistry