Question from AtarNotes Topic Tests

[fishbiscuit]

Question 10 from Chemical Monitoring and Management Test 1:

A gas is produced when 10.0 g of zinc is placed in 0.50 L of 0.20 mol/L nitric acid. Calculate the volume of gas produced at 25 degrees and 100kPa. Include a balanced chemical equation in your answer.


I found Zn moles to be 0.153 but then found HNO3 moles to be 0.1
I assumed HNO3 was the limiting reagent so I used that for my mole ratio but the answers used Zn moles for the mole ratio.

I’m confused about which is right - I thought we had to always find limiting reagents and use the one with the lowest moles for our mole ratio.

If my knowledge about limiting reagents is wrong please correct me.

Thank you!

[KT Nyunt]

Question 10 from Chemical Monitoring and Management Test 1:

A gas is produced when 10.0 g of zinc is placed in 0.50 L of 0.20 mol/L nitric acid. Calculate the volume of gas produced at 25 degrees and 100kPa. Include a balanced chemical equation in your answer.


I found Zn moles to be 0.153 but then found HNO3 moles to be 0.1
I assumed HNO3 was the limiting reagent so I used that for my mole ratio but the answers used Zn moles for the mole ratio.

I’m confused about which is right - I thought we had to always find limiting reagents and use the one with the lowest moles for our mole ratio.

If my knowledge about limiting reagents is wrong please correct me.

Thank you!

I got the same calculations as you and I'm very sure that the limiting agent is the reagent with the least amount of moles. Thus, you're right, the amount of moles of the limiting reagent would be the moles you use in your calculations as that is the number of moles of reagents reacted. I think there's a good chance the answers are wrong. (Unless we're both wrong)

My answer would have been:

Spoiler

Zn_(s) + 2HNO_3(aq) --> Zn(NO₃)_2(aq) + H_2(g)
1.24 L of H₂

[fishbiscuit]

I got the same calculations as you and I'm very sure that the limiting agent is the reagent with the least amount of moles. Thus, you're right, the amount of moles of the limiting reagent would be the moles you use in your calculations as that is the number of moles of reagents reacted. I think there's a good chance the answers are wrong. (Unless we're both wrong)

My answer would have been:

Spoiler

Zn_(s) + 2HNO_3(aq) --> Zn(NO₃)_2(aq) + H_2(g)
1.24 L of H₂

Woo woo I got that answer too! Glad we’re both on the same page