How can you tell that Sodium chlorate(v) has the formula NaClO3?

Question

Just cant remember how to solve these types of chemistry questions. Question asks you to suggest the formula of sodium chlorate(v) - something to do with the (v) but what?

Thank you!

Answer 1

The (V) IS important. When you have a cation or an anion with a element having a variable oxidation state in it, the actual oxidation state is denoted using roman numerals.

V stands for 5, so the oxidation state of the Cl is +5.

So, knowing that sodium has to be Na+, then the anion has to have a charge of -1.

Now, the algebraic sum of the oxidation numbers has to equal the charge on the ion.Since the Cl has an oxidation state of +5, and O always has an oxidation state of -2 (except in peroxides, -1, and when linked to F), then the only way for +5 to be brought overall to -1 is to have 3 x -2's for a total of -6...and thus +5 and -6 is -1.

To elaborate a little bit on the use of the roman numeral,
sodium chlorate (I) is NaClO, where the Cl has an oxidation state of +1
sodium chlorate (III) is NaClO2, where the Cl has an oxidation state of +3, and so on.

Other examples, sulfate(IV), which is SO32- (S oxidation state +4) and sulfate(VI), which is SO42- (S oxidation state +6). Then to the cation into the mixture, you can have copper (I) sulfate (IV), which is Cu2SO3, or copper (II) sulfate (VI), which is CuSO4.

Answer 2

Sodium Chlorate Formula

Answer 3

Sodium Chlorate V

Answer 4

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RE:
How can you tell that Sodium chlorate(v) has the formula NaClO3?
Just cant remember how to solve these types of chemistry questions. Question asks you to suggest the formula of sodium chlorate(v) - something to do with the (v) but what?

Thank you!

Answer 5

The (v) has nothing to do with it (I don't even know what the v is supposed to mean.)

For formulas you need to know (i.e. memorize)

symbols and charges for the elements
formulas and charges for the common radicals (aka polyatomic ions).

The periodic table gives some help for elements since charge (valence) follows a pattern.

To write a correct formula you first write the positive part first (in this case the sodium) then the negative part (in this case the chlorate).

Then you add subscripts so that the total positive charge and total negative charge are equal (producing a neutral compound)

Na is 1+ and chlorate (ClO3) is 1- so it only takes one of each to make a neutral compound.

NaClO3

Answer 6

Let's first discuss the use of Roman numerals...usu. only used with transition metals that have more than one possible charge (Cu, Zn, Pb...). Another less common, but nec. for this question, convention is oxidation state of the Cl. You would know this is the case when the Roman numeral follows the chlorate.

How to remember naming polyatomic ions (mainly the salts of acids):

Metals in column 1 always make +1 ions/charge and those in column 2 always make +2 ions/charge. You need to memorize the naming rules of acids...just memorize these rules:

-ite always has one fewer oxygen than -ate
for some polyatomic ions like the chlorate family, you also need
For a few poly. ions, you also need to remember that hypo-....-ite means one fewer oxygen than -ite (remember than hypo- means below or under) and per-....-ate means one more oxygen than the -ate.

The other key to memorizing ions is to know that the charge will ALWAYS be the same for each species:

hypochlorite (HCO)-1
chlorite (HCO2)-1
chlorate (HCO3)-1
perchlorate (HCO4)-1

Oxidation state of the chlorine in the polyatomic anion has absolutely nothing to do with formula writing, since the charge for all of the chloric acid species is the same!!!!

Answer 7

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Sodium + Chlorine 2Na + Cl2 -> 2NaCl Calcium + Chlorine Ca + Cl2 -> CaCl2 Aluminum + Chlorine 2Al + 3Cl2 -> 2AlCl3 Written out and balanced, the CL by itself needs to be Cl2, I forgot who's rule it was, but it applies to most gasses I think.