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3 years ago

Which process is an example of a chemical change?

Chemistry

2 answers:

Ivanshal [37]3 years ago

8 0

A metal rail rusting in damp weather.

jonny [76]3 years ago

3 0

Answer:

The correct answer is :<u><em>a metal railing rusting in damp weather</em></u> is an example of a chemical change.

Explanation:

Physical property is defined as the property of a substance which becomes evident during physical changes. Example: Melting point

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.

Example: Melting of ice

Chemical property is defined as the property of a substance which becomes evident during chemical changes. Example: Reactivity with other substances

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.

Example: Corrosion of iron called as rusting.

Rust is ferric oxide $Fe_2O_3$ .

$4Fe+3O_2\righatarrow 2Fe_2O_3$

A metal railing rusting in damp weather is an example of chemical change because composition of an iron rail is changing.

$4Fe+3O_2\rightarrow 2Fe_2O_3$

Where as other examples given are the examples of physical change.

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A gas has a volume of 5.0 L at a pressure of 50 KPa. What happens to the volume when the pressure is increased to 125?

Alexeev081 [22]

The volume becomes two. You have to use the equation P1 x V1 = P2 x V2
P is pressure and V is volume.
P1 = 50 P2 = 125
V1 = 5 V2 = v (we don't know what it is)
Then set up the equation:
50 times 5 = 125 times v
250 = 125v
the divide both sides by 125 and isolate v
2 = v
Therefore the volume is decreased to 2.
Also, Boyle's Law explains this too: Volume and pressure are inversely related, This means that when one goes up the other goes down (ie when pressure increases volume decreases and vice versa). Becuase the pressure went up from 50 KPa tp 125 KPa the volume had to decrease.

7 0

3 years ago

How many grams of PbBr2 will precipitate when excess CuBr2 solution is added to 77.0 mL of 0.595 M Pb(NO3)2 solution?Pb(NO3)2(aq

Alexxx [7]

Answer:

16.89g of PbBr2

Explanation:

First, let us calculate the number of mole of Pb(NO3)2. This is illustrated below:

Molarity of Pb(NO3)2 = 0.595M

Volume = 77mL = 77/1000 = 0.077L

Mole =?

Molarity = mole/Volume

Mole = Molarity x Volume

Mole of Pb(NO3)2 = 0.595x0.077

Mole of Pb(NO3)2 = 0.046mol

Convert 0.046mol of Pb(NO3)2 to grams as shown below:

Molar Mass of Pb(NO3)2 =

207 + 2[ 14 + (16x3)]

= 207 + 2[14 + 48]

= 207 + 2[62] = 207 +124 = 331g/mol

Mass of Pb(NO3)2 = number of mole x molar Mass = 0.046 x 331 = 15.23g

Molar Mass of PbBr2 = 207 + (2x80) = 207 + 160 = 367g/mol

Equation for the reaction is given below:

Pb(NO3)2 + CuBr2 —> PbBr2 + Cu(NO3)2

From the equation above,

331g of Pb(NO3)2 precipitated 367g of PbBr2

Therefore, 15.23g of Pb(NO3)2 will precipitate = (15.23x367)/331 = 16.89g of PbBr2

8 0

3 years ago

Match the symbol for each element with the name of the element. 1. hydrogen K 2. helium Mg 3. sodium He 4. magnesium H 5. potass

insens350 [35]

Answer:

1. hydrogen - H

2. helium - He

3. sodium - Na

4. magnesium - Mg

5. potassium - K

Explanation:

Hydrogen is the element of group 1 and first period. The atomic number of hydrogen is 1 and the symbol of the element is H.

The electronic configuration of the element hydrogen is:-

$1s^1$

Helium is the element of group 18 and first period. The atomic number of helium is 2 and the symbol of the element is He.

The electronic configuration of the element helium is:-

$1s^2$

Sodium is the element of group 1 and third period. The atomic number of sodium is 11 and the symbol of the element is Na.

The electronic configuration of the element sodium is:-

$1s^22s^22p^63s^1$

Magnesium is the element of group 2 and third period. The atomic number of magnesium is 12 and the symbol of the element is Mg.

The electronic configuration of the element magnesium is:-

$1s^22s^22p^63s^2$

Potassium is the element of group 1 and forth period. The atomic number of potassium is 19 and the symbol of the element is K.

The electronic configuration of the element potassium is:-

$1s^22s^22p^63s^23p^64s^1$

5 0

3 years ago

An isotonic salt solution is 0.90% (w/w) nacl in water. how many grams of nacl are contained in 1.00 kg of such a solution?

Fed [463]

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2 years ago

When energy is transferred from the air to the water, what happens to most of the energy? A. It travels through the water. B. It

BigorU [14]

Answer: Option (A) is the correct answer.

Explanation:

When energy is transferred from the air to the water then energy is absorbed by the water molecules.

This energy travels through one molecule of water to another molecule of water by the process of convection.

Thus, we can conclude that when energy is transferred from the air to the water, then it travels through the water.