Which molecules are pure elements?

the molecules formed by one kind of atom are pure elements

Explanation:

1) The definition of molecules is the covalent bonding of two or more atoms.

2) Under that definition you must have at least two atoms to be considered a molecule.

3) Pure elements are the 118 elements that you find in the periodic table: each contain only one kind of atom.

4) Then, molecules of pure elements, are two or more atoms of the same kind linked by covalent bonds.

5) With that these some examples of molecules that are pure elements:

i) O₂

ii) N₂

iii) F₂

iv) Cl₂

v) Br₂

vi) O₃

6) And here some examples of molecules that are not pure elements (there are many, many):

i) CH₄

ii) CH₃CH₂CH₃

ii) CH3CH₂CH₂CH₂CH₂CH₂CH₂CH₃

7) Note that ionic compounds are excluded of the definition of molecules, since they are not formed by covalent bonds but by ionic bonds. For example, NaCl is not a molecule.

A. 257600g (i.e 257.6 Kg) of CaO were produced.

B. 202400g (i.e 202.4 Kg) of CO2 were produced.

Explanation:

We'll begin by calculating the mass of CaCO3 present in 5×10² Kg of lime stone. This is illustrated below:

From the question given, the lime stone contains 92% of CaCO3.

Mass of CaCO3 = 92% x 5×10² Kg

Mass of CaCO3 = 92/100 x 5×10² Kg

Mass of CaCO3 = 460 Kg

Therefore, 460 kg of CaCO3 is present in the lime stone.

Next, we shall determine the mass of CaCO3 that was heated and the masses of CaO and CO2 produced from the balanced equation. This is illustrated below:

CaCO3(s) —> CaO(s) + CO2(g)

Molar mass of CaCO3 = 40 + 12 + (16x3) = 100g/mol

Mass of CaCO3 from the balanced equation = 1 x 100 = 100g

Molar mass of CaO = 40 + 16 = 56g

Mass of CaO from the balanced equation = 1 x 56 = 56g

Molar mass of CO2 = 12 + (2x16) = 44g/mol

Mass of CO2 from the balanced equation = 1 x 44 = 44g

Summary:

From the balanced equation above,

100g of CaCO3 were heated to produce 56g of CaO and 44g of CO2.

A. Determination of the mass of quick lime, CaO produced by heating 5×10² Kg of lime stone.

5×10² Kg of lime stone contains 460 Kg (i.e 460×10³ g) of CaCO3.

From the balanced equation above,

100g of CaCO3 were heated to produce 56g of CaO.

Therefore, 460×10³g of CaCO3 will be heated to produce = (460×10³ x 56)/100 = 257600g of CaO.

Therefore, 257600g (i.e 257.6 Kg) of CaO were produced.

B. Determination of mass of carbon dioxide, CO2 produced by heating 5×10² Kg of lime stone.

5×10² Kg of lime stone contains 460 Kg (i.e 460×10³ g) of CaCO3.

From the balanced equation above,

100g of CaCO3 were heated to produce 44g of CO2.

Therefore, Therefore, 460×10³g of CaCO3 will be heated to produce = (460×10³ x 44)/100 = 202400g of CO2.

Therefore, 202400g (i.e 202.4 Kg) of CO2 produced.