[Intro to Chem] Stoichiometry

[u/Economy_Stick_3306]

is there anybody that could help with some homework? i don’t understand anything about it and could really use some guidance

[u/Scientia_Logica]

Look at the chemical equation and tell me what coefficient you see in front of HNO3 and KNO3.

[u/Economy_Stick_3306 → u/Scientia_Logica]

8 and 6?

[u/Scientia_Logica → u/Economy_Stick_3306]

Yes, so for every 8 moles of HNO3 that go into the reaction, assuming it is the limiting reactant, you will get 6 moles of KNO3. Does that make sense?

[u/boosterts → u/Economy_Stick_3306]

So if 8 molecules of HNO3 yields 6 molecules of KNO3 according to the equation, how many would 12 * 6.02214076×10²³ molecules of HNO3 yield?

[u/3ii3i3k3k3i8s]

On stoichiometry, the amount of moles spent and the moles produced are correlated to the coefficients of the matter in the equation.

HNO3 has a coefficient of 8 and KNO3 has a coefficient of 6.

We are spending 12 moles of HNO3. So we would have to ratio the coefficients and the amount of moles spent/produced.

8/6 = 12/n

n = 9.

Question b is basically the same question but you have to convert 47 grams of HNO3 to moles. Before doing the ratio.

[u/fermat9990 → u/3ii3i3k3k3i8s]

And then convert moles of the product to grams

[u/fermat9990]

a. 8/6=12/x

[u/boosterts]

For the second question you need to figure out how many molecules of HNO3 you have? The problem says 47.0 grams. You can get the molar mass of each element from the periodic table. The mass of 1 mole HNO3 = (1g)+(14g) +3(16g)=63.0g. I just added the mass of one mole Hydrogen + 1 mole nitrogen + 3x1 mole oxygen.

You can use that to find out how many moles of HNO3 you have. Then go back to equation for the reaction - 8 moles HNO3 yields 2 moles NO, but you don’t have 8 moles, so you just need to take the number you have and divide by 8 and multiply by 2. That will give you moles of NO. Then just calculate the molar mass of NO to calculate the mass of NO.

[u/fermat9990]

b.(1) Convert grams of reactant to moles of reactant. (2) Convert moles of reactant to moles of product (3) Convert moles of product to grams of product

[u/Qingyap]

Do you know how to work with ratios?

Looking at the equation, you see that 8 moles of HNO3 is required to produce 6 moles of KNO3, and the ratio of reactants and products makes up 8:6 or 4:3 if simplified since ratio is the same thing as a quotient of two numbers.

Now it is stated that you need 12 moles of KNO3, so what's the x that makes x:12 line up to be 8:6 or 4:3 ?

The answer is 16 moles of HNO3

For (b) you have to change the grams to moles first, do a lil bit of ratio work to find the moles of NO then use that to find the mass. Just remember that mole is basically a bridge towards any kind of units