Question

Did an oxidation-reduction reaction occur in the reaction between copper sulfate and sodium sulfide?

CuSO4 + Na2S → CuS + Na2SO4

A.
This is a redox reaction because copper gained electrons.
B.
This is a redox reaction because sodium lost electrons.
C.
This is a redox reaction because sulfur gained electrons.
D.
This is not a redox reaction because no electrons were transferred.
E.
This is not a redox reaction because oxygen did not gain electrons.


In which reaction is precipitation occurring?

A.
MgCl2(aq) + CuSO4(aq) → CuCl2(aq) + MgSO4(aq)
B.
CdSO4(aq) + K2S(aq) → CdS(s) + K2SO4(aq)
C.
NaOH(aq) + NH4Cl(aq) → NaCl(aq) + NH4OH(aq)
D.
K2SO4(aq) + NaOH(aq) → K2OH(aq) + NaSO4(aq)
E.
HNO3(aq) + KOH(aq) → KNO3(aq) + H2O(l)

Answer 1

1. It's not gonna be A, B, or C because  redox means when the electrons transfer both ways and a b and c dont show that. Bw d and E i'd go for D.

for 2.

I'd say B  because both reactants are acqueous while 1 product is solid so it would probably precipitate.

good luck dadddddd

Answer 2

Redox question

Answer:

D. This is not a redox reaction because no electrons were transferred.

Explanation:

We can check whether a reaction is a redox reaction by determining the oxidation number of each atom on both sides of the arrow.

$\stackrel{\hbox{+2}}{\hbox{Cu}}\stackrel{\hbox{+6}}{\hbox{S}}\stackrel{\hbox{-2}}{\hbox{O}}_{4} + \stackrel{\hbox{+1}}{\hbox{Na }}_{2}\stackrel{\hbox{-2}}{\hbox{S}} \longrightarrow \stackrel{\hbox{+2}}{\hbox{Cu}}\stackrel{\hbox{-2}}{\hbox{S}} + \stackrel{\hbox{+1}}{\hbox{Na}}_{2}\stackrel{\hbox{+6}}{\hbox{S}}\stackrel{\hbox{-2}}{\hbox{O}}_{4}$

The oxidation number does not change for any atom, so this is not a redox reaction.

Precipitation question

Answer:

B.  CdSO₄(aq) + K₂S(aq) → CdS(s) + K₂SO₄(aq)

Explanation:

A precipitation reaction occurs when an insoluble solid forms from the reaction of two substances in a solution.

This is the only reaction that forms a solid from two soluble reactants.