I have missed out on a lot of school due to hospitilization and I'm lost in chemistry?

Question

I am currently working on balancing chemical and formula equation and we are doing something with oxidation numbers. I understand the basics, but when she throws on single and double replacement equations, I'm lost again. If someone can explain this to me that would be great. Thanx in advance

Answer 1

In a single replacement reaction, an uncombined element (such as zinc, Zn) reacts with a compound (e.g., hydrochloric acid, HCl), taking the place of one of the elements in the compound (hydrogen, H, in this case). the result is a compound that includes the formerly uncombined element (zinc chloride, ZnCl2) and an element that was part of the former compound but got replaced (hydrogen, which is now in gas form, H2).

To balance the equation, you need to Cl's for each Zn, so you put one Zn and 2 HCls on the left and see what comes out on the right:

Zn + 2 HCl -> ZnCl2 + H2

Zinc replaced hydrogen. Single replacement reaction.

In a double replacement reaction, you have two compounds, and the elements "change partners."
Example: Zinc Carbonate (ZnCO3) and Hydrochloric Acid (HCl)

The most powerful oxidizing agent in the combination (Cl) will combine with the most powerful reducing agent (Zn). This leaves the less powerful oxidizing agent (carbonate, CO3) to combine with the less powerful reducing agent (H). Again, we will need to Cls for each Zn, so the equation balances as follows:

ZnCO3 + 2 HCl -> ZnCl2 + H2CO3

Zinc has replaced hydrogen, and hydrogen has replaced zinc.
Also, chlorine has replaced carbonate, and carbonate has replaced chlorine.

Result: double replacement.