which equation represents an oxidation-reduction reaction?
1.HCl+KOH-->KCl+H2O
2.4HCl+MnO2-->MnCl2+2H2O+Cl2
3.2HCl+CaCO3-->CaCl2+H2O+CO2
4.2HCl+FeS-->FeCl2+H2S
Well, I could try to give you a serious answer, but where's the fun in that? So, let's crack a joke instead!
Why did the chemist break up with the biologist?
Because there was no "chemistry" between them!
Now, let's get back to business. The equation that represents an oxidation-reduction reaction is option 2: 4HCl+MnO2 --> MnCl2+2H2O+Cl2.
The equation that represents an oxidation-reduction reaction is:
2HCl + MnO2 → MnCl2 + 2H2O + Cl2
In this equation, chlorine (Cl) is oxidized from -1 in HCl to 0 in Cl2, and manganese (Mn) is reduced from +4 in MnO2 to +2 in MnCl2.
To determine which equation represents an oxidation-reduction (redox) reaction, we need to identify the substances that are undergoing oxidation and reduction.
In a redox reaction, oxidation and reduction always occur together. Oxidation involves the loss of electrons, while reduction involves the gain of electrons.
Let's analyze each equation:
1. HCl + KOH --> KCl + H2O: In this equation, hydrogen chloride (HCl) and potassium hydroxide (KOH) combine to form potassium chloride (KCl) and water (H2O). There is no change in the oxidation states of the elements involved; therefore, this is not a redox reaction.
2. 4HCl + MnO2 --> MnCl2 + 2H2O + Cl2: In this equation, manganese dioxide (MnO2) reacts with hydrochloric acid (HCl) to produce manganese chloride (MnCl2), water (H2O), and chlorine gas (Cl2). The oxidation state of manganese changes from +4 in MnO2 to +2 in MnCl2, indicating reduction. Chlorine changes from -1 in HCl to 0 in Cl2, indicating oxidation. This equation represents a redox reaction.
3. 2HCl + CaCO3 --> CaCl2 + H2O + CO2: In this equation, hydrochloric acid (HCl) reacts with calcium carbonate (CaCO3) to produce calcium chloride (CaCl2), water (H2O), and carbon dioxide (CO2). There is no change in the oxidation states of the elements involved; therefore, this is not a redox reaction.
4. 2HCl + FeS --> FeCl2 + H2S: In this equation, hydrochloric acid (HCl) reacts with iron sulfide (FeS) to produce iron chloride (FeCl2) and hydrogen sulfide (H2S). There is no change in the oxidation states of the elements involved; therefore, this is not a redox reaction.
Based on the analysis above, the equation that represents an oxidation-reduction reaction is:
2HCl + MnO2 --> MnCl2 + 2H2O + Cl2
The easy, but painful when you're just learning, way is to go through methodically and write the oxidation state of EACH atom, then compare on both sides to see if anything has changed. For example, I'll do the first one BUT I can't write over or under the atoms/ions. I'll do it step wise.
HCl + KOH ==> KCl + H2O
1. HCl. H is +1; Cl is -1.
2. KOH. K is +1; O is -2; H is +1
3. KCl. K is +1; Cl is -1.
4. H2O. Each H is +1; O is -2
Compare and you will see there were no changes; therefore, #1 is not a redox reaction.
Do you know how to determine the oxidation state? Here is a good site to get you started.
http://www.chemteam.info/Redox/Redox-Rules.html