the nucleus is an organelle containing the cell's chromosomes
The correct answer is 3) 2CO2(g) ⇄ 2CO(g) + O2(g)
this is the correct one because it is a decomposition reaction and all the number of atoms is equal on both sides.
there are 2 C atoms on both sides.
and 4 O atoms on both sides.
and 1) the atoms numbers are equal on both sides but not correct as it not a
correct number as it has 1/2 O2.
and 2) CO2(g) ⇆ CO(g) + O2
the number of O atoms is not equal on both sides of the equation.
we have 2 O atoms on the left side and 3 O atoms on the right side.
so, this not a balanced equation.
4) also not correct 2CO(g) + O2 ⇆ 2CO2
as it is not a decomposition reaction and the 2CO & O2 are as reactants not products.
so the correct answer is 3) 2CO2(g) ⇆ 2CO(g) + O2(g)
The answer you are looking for is the second option, "<span>Matter can be divided into two groups: pure substances and mixtures."
A pure substance can describe a pure element or chemically bonded elements. A pure substance cannot be broken down into further substances. An example of these would be Fe (iron) or O2 (oxygen).
A mixture is a structure made from physically combining different non-bonded substances. An example of a mixture is blood.
Both pure substances and mixtures are types of matter.</span>
Answer: 
Explanation:
Complete ionic equation : In complete ionic equation, all the substance that are strong electrolytes and are represented in the form of ions.
The complete ionic equation will be:
Net ionic equation : In the net ionic equations, we do not not include the spectator ions in the equations.
Spectator ions : The ions present on reactant and product side which do not participate in a reactions. The same ions present on both the sides.
In this equation, 
and 
are the spectator ions.
By removing the spectator ions from the balanced ionic equation, we get the net ionic equation.
The net ionic equation will be:
