Video Transcript
Nitric acid can be produced by
mixing sodium nitrate with sulfuric acid and heating the mixture to 83 degrees
Celsius. Which of the following is the
correct chemical equation for this reaction? (A) NaNO2 plus H2SO4 produces NaSO3
plus H2NO3. (B) Na(NO3)2 plus H2SO4 produces
NaSO4 plus two HNO3. (C) NaNO3 plus HSO4 produces NaSO4
plus HNO3. (D) NaNO3 plus H2SO4 produces
NaHSO4 plus HNO3. Or (E) Na2(NO3) plus two H2SO4
produces two NaSO4 plus H2NO3 plus H2.
This question describes a reaction
in words and then asks us to find the chemical equation that matches it. To select the correct chemical
equation, we will need to determine the chemical formulas of the compounds named in
the question. The simplest compound to start with
is sodium nitrate. Sodium nitrate is an ionic compound
made up of a sodium ion and a nitrate ion. Since the two ions have opposite
charges, a one plus ion and a one minus ion, we can combine them in a one-to-one
ratio to determine the chemical formula of sodium nitrate, NaNO3.
In our answer choices here, the
first reactant, the one that should be sodium nitrate, only has the correct chemical
formula in answer choice (C) and (D). So we can eliminate the other three
answer choices from consideration. There are two acids in this
problem: nitric acid and sulfuric acid. And we can determine their chemical
formulas by looking at a certain rule. The relevant rule for naming acids
here is that if an ion’s name ends in -ate, the name of the acid it forms ends in
-ic acid.
For example, in this problem, we
have nitric acid. Based on the rule, we know that the
anion of nitric acid is a nitrate ion. We looked at the nitrate ion
earlier. Its chemical formula is NO3−. To turn it into an acid, all we
need to do is add enough hydrogens to counteract the negative charge. In this case, it takes only
one. The chemical formula of nitric acid
is HNO3. Both remaining answer choices have
the correct formula for nitric acid as one of the products in the chemical
equation. So we need to look at sulfuric
acid.
Following the same pattern as
before, we start with sulfuric acid. Following the naming rule, the
anion should end in -ate, a sulfate ion. The sulfate ion has a chemical
formula of SO42−. Since the sulfate ion has a two
minus charge, we need to add two hydrogen ions to end up with a neutral
compound. If we compare the second reactant
of each of the remaining answer choices, we can see that only answer choice (D) has
the correct chemical formula for sulfuric acid, H2SO4. Choice (D) is the correct
answer. It correctly displays NaNO3 as the
chemical formula for sodium nitrate, H2SO4 as the chemical formula for sulfuric
acid, and HNO3 as the chemical formula for nitric acid. The last compound, sodium hydrogen
sulfate, is not mentioned in the question, but it is a product of this reaction.
So, “Which of the following is the
correct chemical equation for this reaction?” That’s the reaction shown in choice
(D). NaNO3 plus H2SO4 produces NaHSO4
plus HNO3.
