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Alex777 [14]
3 years ago
6

Whic number of the periodic table is the atomic number and which number is the atomic mass?

Chemistry
1 answer:
Anettt [7]3 years ago
5 0

Answer:

The mass number (represented by the letter A) is defined as the total number of protons and neutrons in an atom. Consider the element helium. Its atomic number is 2, so it has two protons in its nucleus.

The atomic mass of a single atom is simply its total mass and is typically expressed in atomic mass units or amu. By definition, an atom of carbon with six neutrons, carbon-12, has an atomic mass of 12 amu.

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An aqueous solution of a certain chemical is found to boil at 104.5 oC. At what temperature is this solution likely to freeze? T
xeze [42]

Answer:

16.4 °C

Explanation:

Boiling point elevation is the phenomenon in which the boiling point of a solvent will increase when another compound is added to it; meaning that athe resultant solution has a higher boiling point than its pure solvent.

Using the ebullioscopic constant,

ΔT = m * i * Kb

Where,

Δ T is the temperature difference between the boiling point of the solution, Temp.f and boiling point of the pure solvent, Temp.i

Kb is the ebulliscope factor of water = 0.510 °C.kg/mol

i is the van hoffs number = 1

m is the molality in mol/kg.

Calculating the molality of the solution,

Temp.i = 100°C

Temp.f = 104.5 °C

= 4.5/(1*0.510)

= 8.8235 mol/kg

Freezing point depression is defined as the decrease in the freezing point of a solvent on the addition of a solute.

Using the same equation, but kf = 1.86 °C.kg/mol

ΔT = m * i * Kf

Temp.i = freezing point of water = 0°C

Temp.f = (8.8235*1.86) - 0

= 16.412 °C

Freezing point of the solution = 16.4 °C

3 0
3 years ago
Which element can expand its valence shell to accommodate more than eight electrons? which element can expand its valence shell
Anvisha [2.4K]
<span>According to octet rule,  atoms with an atomic number less than 20 tend to combine  with other atom such that both of these atoms have eight electrons in their valence shells, which gives them the same electronic configuration as that of noble gas.

However, there are few compound that donot obey octel rule. Among the elements mentioned above i.e. oxygen and helium obeys octet rule.

In case of nitrogen, oxide of nitrogen (like NO and NO2) have incomplete octet. 

While there are few compounds of Br wherein Br has expanded octet. For example, in BrF5, Br has 12 electrons in valence shell. </span>
3 0
3 years ago
Read 2 more answers
How does this article relate to me?
mario62 [17]
I cant help unless there is an article..
4 0
3 years ago
Read 2 more answers
Aluminum can react with oxygen gas to produce aluminum oxide, what time of reaction is this?
Helga [31]
This is known as a synthesis reaction. A+B->C
Hope this helps!
3 0
3 years ago
Three common ores of iron are FeO, Fe2O3, and Fe3O4. Iron ores are often reduced to elemental iron by heating in the presence of
brilliants [131]

Answer:

Answers are explained below

Explanation:

(a)

Oxidation number of iron :

FeO = +2

Fe2O3= +3

Fe3O4 = +2 and +3 since Fe3O4 is the mixture of FeO and Fe2O3.

(b) FeO + CO ----> Fe (s) + CO2

(c) In a pure iron metallic bond is exist between the particles of Fe. But in the form of ore metals forms ionic bond with the non-metals.

Hence the properties vary.

Yes carbon steel has greater strength than that of pure iron but retains the property of iron because no chemical reaction occurs between carbon and iron.

d)

Mixing of carbon in iron is a type of physical change since there is no chemical reactions occur between the carbon and iron. Carbon atoms diffuses in the place between the iron atoms.

(f) One of the property of non-metals are brittleness. It is non ductile .

So when the percentage of carbon increases its atoms also occupying more and more free places.

And increasing the brittleness. So the iron becomes less ductile.

e)

6 0
3 years ago
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