Balance the following equations, and then write the net...

Balance the following equations, and then write the net ionic equation: (a) $\mathrm{Zn}(\mathrm{s})+\mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{H}_{2}(\mathrm{g})+\mathrm{ZnCl}_{2}(\mathrm{aq})$ (b) $\mathrm{Mg}(\mathrm{OH})_{2}(\mathrm{s})+\mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{MgCl}_{2}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\ell)$ (c) $\mathrm{HNO}_{3}(\mathrm{aq})+\mathrm{CaCO}_{3}(\mathrm{s}) \rightarrow$ $\mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\ell)+\mathrm{CO}_{2}(\mathrm{g})$ (d) $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{S}(\mathrm{aq})+\mathrm{FeCl}_{2}(\mathrm{aq}) \rightarrow \mathrm{NH}_{4} \mathrm{Cl}(\mathrm{aq})+\mathrm{FeS}(\mathrm{s})$

Balance the following equations, and then write the net ionic equation:
(a) $\mathrm{Zn}(\mathrm{s})+\mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{H}_{2}(\mathrm{g})+\mathrm{ZnCl}_{2}(\mathrm{aq})$
(b) $\mathrm{Mg}(\mathrm{OH})_{2}(\mathrm{s})+\mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{MgCl}_{2}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\ell)$
(c) $\mathrm{HNO}_{3}(\mathrm{aq})+\mathrm{CaCO}_{3}(\mathrm{s}) \rightarrow$
$\mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\ell)+\mathrm{CO}_{2}(\mathrm{g})$
(d) $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{S}(\mathrm{aq})+\mathrm{FeCl}_{2}(\mathrm{aq}) \rightarrow \mathrm{NH}_{4} \mathrm{Cl}(\mathrm{aq})+\mathrm{FeS}(\mathrm{s})$

Key Concepts

Balancing Chemical Equations

This concept involves ensuring that the number of atoms for each element is the same on both sides of a chemical equation. It is based on the law of conservation of mass, which dictates that matter cannot be created or destroyed in a chemical reaction. Achieving a balanced equation is essential for determining the correct stoichiometric coefficients, which are used to relate the amounts of reactants and products involved in the reaction.

Net Ionic Equations

Net ionic equations focus on the species that are directly involved in the chemical change, stripping away all spectator ions. This simplifies the reaction to its fundamental chemical process, highlighting the actual transformation that occurs. It is particularly useful in aqueous reactions where many compounds dissociate into ions, allowing for a clearer picture of the underlying reaction mechanism.

Spectator Ions

Spectator ions are ions present in the reaction mixture that do not participate directly in the chemical change. They remain in solution unchanged and are present on both the reactant and product sides of the complete ionic equation. Identifying spectator ions is a crucial step in forming net ionic equations, as their removal simplifies the equation without affecting the overall reaction.

States of Matter in Chemical Reactions

The states of matter (solid, liquid, gas, aqueous) are critical in chemical equations because they provide insight into the physical properties of the reactants and products. For example, knowing whether a substance is in aqueous solution, a precipitate (solid), a gas, or a liquid can help predict reaction outcomes and determine which compounds will dissociate into ions or remain intact. This understanding is essential for correctly balancing equations, forming ionic equations, and properly identifying spectator ions.

Transcript

00:01 Hello everyone, and thanks for joining as we balance chemical equations and then write the net ionic equations.

00:07 Let's get started.

00:09 We have four of these to do.

00:10 Our first equation, we are looking at solid zinc reacts with aqueous hydrochloric acid to produce gaseous hydrogen and aqueous zinc chloride.

00:24 And as i mentioned, our first step will be to balance this chemical equation.

00:30 This one is actually pretty easy to balance because i can see i have two hydrogens and two chlorides on this side, and i only have one in each of these.

00:39 So putting a two here will accomplish all the balancing i need to do.

00:45 Okay, next on our agenda, we are going to write, for this one, we're going to write our ionic, our complete ionic equation.

00:54 And remember to do that, we dissociate our aqueous substances.

00:58 Let's begin.

01:00 I'll have my zinc.

01:02 It's not aqueous, so i leave it.

01:06 The hydrochloric acid needs to be split into two hydrogen ions and two chloride ions.

01:19 The hydrogen gas is good as is, and the zinc chloride dissociates into the zinc ion and two chloride ions.

01:33 Now remember our next step is to get rid of our spectator ions, and in this case, our spectator ions are these two.

01:45 Okay, now you will often see this, and i'm going to continue this in a less bright color, you'll often see this type of single replacement reaction represented just as follows.

02:08 But that's not the way that this particular form.

02:14 Of our textbook wants us to look at this.

02:17 Remember that in our textbook, these hydrogens are going to be represented as hydronium ions.

02:28 And do, if you will, make this work.

02:32 That means i had to add 2h2o's to this side and i will also have to add 2h2os to this side.

02:45 Okay.

02:46 And then we just do the same thing for everything else.

02:52 So what i've represented in purple here is the correct answer for this portion of the question.

03:03 There's a plus there.

03:04 That's not very representative.

03:06 Very good to read.

03:12 Plus 2h2o and that is a liquid.

03:25 I'm going to put the l down there.

03:26 Okay, that's problem one.

03:29 Now, let's begin with problem two.

03:33 In this substance, we're given solid magnesium hydroxide.

03:37 Reacting again with hydrochloric acid to produce aqueous magnesium chloride and water.

03:43 First step, balance.

03:46 And to balance this chemical equation, make sure i got my pen on here, i can see again i have two hydrogens and two chlorines on this side, so i need to fix that by putting a two right there.

04:00 Now, that does, that's specifically for the chlorines.

04:05 Now i have two hydrogens and two hydrogens represented for a total, of four, so i'm also going to put a two right here.

04:14 And that'll take care of my oxygens.

04:16 Now i have two oxygens on this side and two oxygens on this side.

04:21 Let me clean this up for writing our net ionic equation.

04:28 For the net ionic equation, we split, again, we're going to split the aqs, so let me begin.

04:36 Magnesium hydroxide is a solid, so we leave it.

04:41 Now i'm going to go ahead, and since this is my h plus, i'm going to write 2h3o plus plus 2 chloride ions, yields mg plus 2 cl minus, plus now i added two waters.

05:13 So now i'm going to have four waters.

05:21 Let's get rid of our spectator ions and our final equation.

05:30 Will be...

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