Transcript CHEMICAL REACTIONS - New Castle High School

CHEMICAL REACTIONS
ChemQuest 28
LiBr + P  Li3P + Br2

Why is bromine written as Br2 on the right
side?

Bromine is a diatomic molecule and always
needs to be bonded to something; even
bonding to itself works.
LiBr + P  Li3P + Br2

Why is it not necessary for LiBr to be
written as LiBr2?

If it were written LiBr2 it would not be a
neutral compound.
Example Equation:
Ca + HNO3  Ca(NO3)2 + H2

What are the reactants in the example
equation in the above information section?

Reactants are written on the left side of the
equation and so the reactants are Ca and
HNO3.
Na + MgCl2  NaCl + Mg

Why can’t NaMg be produced?

Na+ cannot bond with Mg2+ because
they are both positive.
Na + MgCl2  NaCl + Mg

Why can’t NaCl2 be produced?

Na+ only requires one Cl-. NaCl2 is not
a neutral compound.
Na + MgCl2  NaCl + Mg

Are NaCl and Mg the only products that
can be produced?

Yes.
Li + Ca3(PO4)2  Li3PO4 + Ca

Why can’t CaLi2 be produced?

Ca2+ and Li+ won’t bond because they
are both positive.
Li + Ca3(PO4)2  Li3PO4 + Ca

Why can’t Li3P be produced?

Although Li3P is neutral, there is no P3- in the
equation. There is only PO43- and we will
almost never be breaking up polyatomic ions
like PO43-.

Don’t mess with polyatomic ions!
Li + Ca3(PO4)2  Li3PO4 + Ca

Are Li3PO4 and Ca the only substances
that can be produced?

Yes.

Write chemical
equations for the
following reactions.

Aluminum sulfate reacts with
barium to produce barium sulfate
and aluminum.

Al2(SO4)3 + Ba  BaSO4 + Al

Magnesium reacts with copper(I)
nitrate to produce magnesium
nitrate and copper.

Mg + CuNO3  Mg(NO3)2 +
Cu

Sodium reacts with calcium
phosphide to produce sodium
phosphide and calcium.

Na + Ca3P2  Na3P + Ca

Phosphorus reacts with sodium
chloride to produce sodium
phosphide and chlorine.

P + NaCl  Na3P + Cl2
(Note that chlorine is diatomic!)

Each of the reactions you wrote in
question 5 follows a similar pattern.
The same pattern is followed by the
equations in questions 3 and 4.
Describe this pattern.

A single atom reacts with a compound
and replaces one of the atoms in that
compound.

How are reactions 5c and 5d different?

Na forms a positive ion (Na+) and
replaces another positive ion, but P
forms a negative ion (P3-) and replaces
another negative ion.

How are reactions 5c and 5d similar?

In both reactions a single atom replaces
another atom from a compound that it is
reacting with.

NaCl + Ag 

AgCl + Na

(note: order is not important, so you
could also write Na + AgCl)

Li + Ca3(PO4)2 

Li3PO4 + Ca

(again, order is not important)