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4 years ago

Compare and contrast physical and chemical changes in matter. Give an example of each type of change.

1 answer:

3 0

Physical Change: A physical change in a substance does not change what the substance is.

An example of this would be water freezing. The water looks and feels different, but it is still water, and it's chemical formula still remains H2O.

Chemical Change: A chemical change is when there is a chemical reaction and a new substance is formed because of that. The composition of the substance changes, and there is usually energy being released or absorbed.

An example of this would be burning wood. In this case, oxygen is reacting with the wood to produce ash, energy, and smoke.

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slamgirl [31]

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3 years ago

Calculate the cell potential for the following reaction as written at 25.00 °C, given that [Cr2 ] = 0.892 M and [Fe2 ] = 0.0150

Effectus [21]

<u>Given:</u>

Concentration of Cr2+ = 0.892 M

Concentration of Fe2+ = 0.0150 M

<u>To determine:</u>

The cell potential, Ecell

<u>Explanation:</u>

The half cell reactions for the given cell are:

Anode: Oxidation

Cr(s) ↔ Cr2+(aq) + 2e⁻ E⁰ = -0.91 V

Cathode: Reduction

Fe2+ (aq) + 2e⁻ ↔ Fe (s) E⁰ = -0.44 V

------------------------------------------

Net reaction: Cr(s) + Fe2+(aq) ↔ Cr2+(aq) + Fe(s)

E°cell = E°cathode - E°anode = -0.44 - (-0.91) = 0.47 V

The cell potential can be deduced from the Nernst equation as follows:

Ecell = E°cell - (0.0591/n)log[Cr2+]/[Fe2+]

Here, n = number of electrons = 2

Ecell = 0.47 - 0.0591/2 * log[0.892]/[0.0150] = 0.418 V

Ans: The cell potential is 0.418 V

8 0

3 years ago

Read 2 more answers

How does a chemical indicator work ?

sukhopar [10]

PH indicators detect the presence of H+ and OH-. They do this by reacting with H+ and OH-: they are themselves weak acids and bases. If an indicator is a weak acid and is coloured and its conjugate base has a different colour, deprotonation causes a colour change.

5 0

4 years ago

Read 2 more answers

If 14.5 g of MnO4- (permanganate) react with manganese (II) hydroxide how many grams of manganese (IV) oxide will be produced? T

Veronika [31]

Answer:

$m_{MnO_2}=21.2gMnO_2$

Explanation:

Hello,

In this case, given the balanced reaction:

$2MnO_4^-+2Mn(OH)_2\rightarrow 4MnO_2+2OH^-+H_2O$

We can see a 2:4 mole ration between permanganate ion (118.9 g/mol) and manganese (IV) oxide (86.9 g/mol), that is why the resulting mas of this last one turns out:

$m_{MnO_2}=14.5gMnO_4^-*\frac{1molMnO_4^-}{118.9gMnO_4^-}*\frac{4MnO_2}{2molMnO_4^-} *\frac{86.9gMnO_2}{1molMnO_2} \\\\m_{MnO_2}=21.2gMnO_2$

Best regards.

5 0

4 years ago

PLEASE HELP ASAP

Inessa05 [86]

The enthalpy change for the reaction 2K + S + K2S using the following thermochemical reactions is mathematically given as

dn=70.7kg

<h3>What is the enthalpy change for the reaction?</h3>

Generally, the equation for the Chemical reaction is mathematically given as

2k+s----->K2S

Therefore

KS+K----->K2S

Therefore

dn=dn1+dn2

dn=32.5+38.2

dn=70.7kg

In conclusion, the enthalpy change is

dn=70.7kg