Answer:
C₂H₄O
CH₃CHO
Explanation:
I'm not sure if you want the molecular formula or the condensed structure, but I will give you both.
Molecular formula:
You have 2 carbons (C₂), 4 hydrogens (H₄), and 1 oxygen (O). The molecular formula will be C₂H₄O.
Condensed Structure:
You have a carbon bonded to three hydrogens (CH₃). This carbon is bonded to a carbon that is bonded to a hydrogen and oxygen (CHO). The condensed structure will be CH₃CHO.
A residue from a gunshot is most likely gun powder, which tells you what kind of bullet was shot and the type of gun that was used to shoot the target/victim/person. Some complications may be that there is more than one gun or weapon which uses that residue, so it may be hard to pinpoint it and the bullet can't really tell you who it is unless there's DNA on the bullet, and the chemicals of the bullet may even destroy evidence.
Answer:
Sodium (Na) has atomic number 11.
Answer:
No reaction
Explanation:
Single-displacement reaction is the chemical reaction in which one metal which has higher negative redox potential replaces the another from it's salt solution.
Thus, Cu cannot replaces zine from its salt as it is less reactive than zince.
However, zinc can replace copper from its salt as:

Because it requires lots of electricity to turn it into an aqueous solution so that electrolysis can be performed on it.