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3 years ago

What is a chemical change?

Chemistry

1 answer:

iris [78.8K]3 years ago

4 0

Answer:

D. A reaction or change in a substance that results in a different substance

Explanation:

Chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances.

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Calculate the quantity of electricity obtained from 2 moles of electrons

Vinil7 [7]

The quantity of electricity : 2 Faraday = 193000 Coulomb

<h3>Further explanation</h3>

Given

2 moles of electrons

Required

The quantity of electricity

Solution

According to Faraday, the amount of current flowing in the electrolysis cell is closely related to the amount of substance that reacts

1 Faraday is the amount of electricity that is passed in the electrolysis cell to obtain 1 mole of electrons. 1 mole of electrons is equivalent to an electric charge of 96500 Coulombs.

The conversion / relationship can be stated as follows:

1 Faraday = 1 mole of electrons = 96500 Coulombs

1 faraday = coulomb / 96500

Can be formulated

Coulomb = Q = I. t so:

$\large {\boxed {\bold {1 \: Faraday \: = \: \dfrac {i \: x \: t} {96500}}}}$

so for 2 moles electrons :

= 2 x 96500 C

= 193000 C

= 2 Faraday

6 0

3 years ago

How often do girls normally experience menstruation a.once every 30 days b. once every 29 c.once every 28 d.once every 27

kramer

Answer:

i think answer is a, every 30 days

5 0

3 years ago

Read 2 more answers

Compare and contrast physical and chemical changes. Give an example of both a physical and chemical change.

kakasveta [241]

Answer:

Physical change is the change that you can see like for example if you turn your light on and off thats physical (thats the best definition for that i can do) and also physical change can go back to its original form it was before. A chemical change is when you do something to something and it cannot be changed back to its original form. Like for example, if you bake a pie, you cannot un-cook all the ingredients to make it raw again

Explanation:

learned this in 5th grade

5 0

3 years ago

A certain liquid has a normal boiling point of and a boiling point elevation constant . A solution is prepared by dissolving som

jek_recluse [69]

The question is incomplete, the complete question is:

A certain substance X has a normal freezing point of $-6.4^oC$ and a molal freezing point depression constant $K_f=3.96^oC.kg/mol$ . A solution is prepared by dissolving some glycine in 950. g of X. This solution freezes at $-13.6^oC$ . Calculate the mass of urea that was dissolved. Round your answer to 2 significant digits.

<u>Answer:</u> The mass of glycine that can be dissolved is $1.3\times 10^2g$

<u>Explanation:</u>

Depression in the freezing point is defined as the difference between the freezing point of the pure solvent and the freezing point of the solution.

The expression for the calculation of depression in freezing point is:

$\text{Freezing point of pure solvent}-\text{freezing point of solution}=i\times K_f\times m$

$\text{Freezing point of pure solvent}=\text{Freezing point of solution}=i\times K_f\times \frac{m_{solute}\times 1000}{M_{solute}\times w_{solvent}\text{(in g)}}$ ......(1)

where,

Freezing point of pure solvent = $-6.4^oC$

Freezing point of solution = $-13.6^oC$

i = Vant Hoff factor = 1 (for non-electrolytes)

$K_f$ = freezing point depression constant = $3.96^oC/m$

$m_{solute}$ = Given mass of solute (glycine) = ?

$M_{solute}$ = Molar mass of solute (glycine) = 75.07 g/mol

$w_{solvent}$ = Mass of solvent = 950. g

Putting values in equation 1, we get:

$-6.4-(-13.6)=1\times 3.96\times \frac{m_{solute}\times 1000}{75.07\times 950}\\\\m_{solute}=\frac{7.2\times 75.07\times 950}{1\times 3.96\times 1000}\\\\m_{solute}=129.66g=1.3\times 10^2g$

Hence, the mass of glycine that can be dissolved is $1.3\times 10^2g$

5 0

3 years ago

Volcanic molten lava pours out and re-hardens back into the rock again. Chemical change or physical change?

gogolik [260]

Answer:

physical change

Explanation:

it it just re hardened

6 0

3 years ago