As I understand it, for someone to commit a mortal sin they must be fully aware that the act is a mortal soul, fully aware of its consequences and freely choose to carry out the sinful act despite the knowledge previously mentioned.
I may be completely wrong but that's as much as I understand at this time. My question then is how can a person be in a state of mortal sin unknowingly if all of the above are required before someone can server their relationship with God?
Isn't basically impossible for someone to be in a state of mortal sin unknowingly?
That is not quite the definition.
Here is the catechism:
1857 For a sin to be mortal, three conditions must together be met: "Mortal sin is sin whose object is grave matter and which is also committed with full knowledge and deliberate consent."131
1858 Grave matter is specified by the Ten Commandments, corresponding to the answer of Jesus to the rich young man: "Do not kill, Do not commit adultery, Do not steal, Do not bear false witness, Do not defraud, Honor your father and your mother."132 The gravity of sins is more or less great: murder is graver than theft. One must also take into account who is wronged: violence against parents is in itself graver than violence against a stranger.
1859 Mortal sin requires full knowledge and complete consent. It presupposes knowledge of the sinful character of the act, of its opposition to God's law. It also implies a consent sufficiently deliberate to be a personal choice. Feigned ignorance and hardness of heart133 do not diminish, but rather increase, the voluntary character of a sin.
1860 Unintentional ignorance can diminish or even remove the imputability of a grave offense. But no one is deemed to be ignorant of the principles of the moral law, which are written in the conscience of every man. The promptings of feelings and passions can also diminish the voluntary and free character of the offense, as can external pressures or pathological disorders. Sin committed through malice, by deliberate choice of evil, is the gravest.
So to sum up, a sin to be mortal must involve grave matter, be committed with knowledge that the act is sinful and full consent (which means that a person must be free to choose to commit the sin or not). It doesn't require a person to be fully aware of the consequences of that sin.
It is easy for a person to meet all of the requirements of mortal sin. The moral law is written on the human heart. Grave matter is objective. Most when sinning give full consent, though some things may temper this to some point, such as addiction etc.
In any case, if a person sins and they have any notion that the sin might be mortal, they should give an immediate act of contrition and partake in the sacrament ASAP. Even with venial sins, a trip to the confessional is a great experience and helps us to be free in Christ and have peace.
Does that help?