When lead(II) sulfide is heated to high temperatures in a stream of pure oxygen gas, solid lead(

When lead(II) sulfide is heated to high temperatures in a...

Key Concepts

Chemical Equations

Chemical equations are symbolic representations of chemical reactions that detail the reactants, products, and, if necessary, the physical states of the substances involved. They provide a concise format for conveying the chemical changes occurring during the reaction.

Balancing Chemical Equations

Balancing chemical equations is the process of ensuring that the number of atoms for each element is conserved on both sides of the reaction. This reflects the fundamental principle of conservation of mass and is an essential skill in accurately representing any chemical transformation.

Reaction Stoichiometry

Reaction stoichiometry involves the quantitative relationships between reactants and products in a chemical reaction. It aids in determining the proportionate amounts of substances necessary for a reaction to proceed completely, which is critical when adjusting the coefficients in a chemical equation.

Oxidation-Reduction (Redox) Reactions

Oxidation-reduction reactions involve electron transfer processes where one species undergoes oxidation (loss of electrons) and another undergoes reduction (gain of electrons). Understanding redox reactions is crucial for analyzing reactions that involve changes in oxidation states and for predicting the behavior of reactants in the presence of an oxidizing agent.

Physical States in Chemical Reactions

Denoting the physical states (solid, liquid, gas, aqueous) of reactants and products in a chemical equation provides important contextual information about the conditions under which a reaction occurs. These state symbols help predict reaction behavior and influence the interpretation of the chemical process.

Transcript

00:02 So to write an unbalanced chemical equation, we need to write the formulas for each of the chemicals involved in the reaction, but we don't actually have to go through in balance.

00:16 So when i read problems like this, my first step is always to look at which chemicals have metals, because i know if a chemical has a metal in it, i'm going to need to write the formula using the charges of the elements.

00:32 And then if there are no metals, but i see some prefixes, that's a clue that i don't need to worry about charges.

00:39 I just need to include the prefix as the elements subscript.

00:45 So lead to sulfide is the first chemical that we have to write the formula for.

00:51 So lead is a metal, and it actually has its charge given to us in the form of that roman numeral two.

01:00 So lead is the symbol pb and it has a plus two charge.

01:08 I knew the symbol for lead because i've been working with chemicals for a long time, but if you are unsure ever of what a chemical symbol is, you can always refer to your periodic table.

01:20 So lead is atomic number 82, and as you can see, its symbol is pb.

01:25 Lead two sulfide, so we got our lead part.

01:28 Now we need the sulfide part.

01:29 So sulfide is referring to sulfur.

01:33 So in a chemical name, the end always starts with an i'd, an 8, or an it.

01:41 So we then have to kind of think about, okay, sulfide, we added an ide to the end of something, and in this case it's sulfur, sulfur, sulfide.

01:52 So the symbol for sulfur is s, and then also if you were looking through, you will have seen some oxygen.

02:00 So the symbol for oxygen is o, which is right above it.

02:03 So we've got some lead, some sulfur, and some oxygen.

02:09 So i know because lead is present, i'm probably going to need charges for the other two elements.

02:14 So looking back at our periodic table, we can find the charges for s and o.

02:19 Now, you may have a periodic table that already has charges written on it.

02:23 If you don't, though, here's a good way to remember it.

02:26 So your noble gases, which on my period table are blue, have a charge of zero.

02:33 Their neighbors, the halogens, have a charge of negative one.

02:37 And in the oxygen family, the group that we need, have a charge of negative two.

02:40 So you just count back, zero, negative one, negative two.

02:44 And then you could keep going.

02:46 Negative three for the nitrogen family, plus or minus four for the carbon family, plus three for boron, plus two for beryllium, plus one for hydrogen.

02:57 But we don't need to go that far.

02:58 We just need oxygen and sulfur.

03:00 And lucky for us, they're the same.

03:01 They're both minus two.

03:03 So i'm going to write those over here.

03:05 Minus two, minus two.

03:07 So now that i know my charges for my elements, i can go ahead and kind of start constructing my formulas.

03:18 So lead two sulfide.

03:19 I know i need lead and sulfur.

03:21 So i'm just going to write their symbols and their charges next to each other.

03:28 And then you may or may not know the crisscross method where you cross down the charge.

03:35 So we would bring a two down here and a two down here.

03:40 Which if we have equal charges, so two to two, we could reduce that or simplify that to one to one.

03:46 So our final formula would be pbs.

03:48 Another way to think about it is that our charges are equal and opposite, the plus two and the minus two.

03:54 So they're going to cancel each other out, which is good because we want our overall charge on our form.

04:00 Formula to be zero.

04:03 So lead two sulfide is pbs.

04:05 We've got that...

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