How do i know a chemical reaction has fully occurred quantitatively? (1 Viewer)

[Shavi Masee]

^^

 

[yourlocaliga]

i think it would just be when all moles of the limiting reagent have been used up when u compare the moles and molar ratio

 

[Shavi Masee]

i think it would just be when all moles of the limiting reagent have been used up when u compare the moles and molar ratio

so if i put the reaction of CaCO3 and HCl
i can measure could calculate (due to how much CaCO3 i'm using) the mass of how much CO2 is being released. and wait for the mass to go down by that amount?

Is that a reliable way...?

 

[wizzkids]

In

How do i know a chemical reaction has fully occurred quantitatively?

Well, that depends on whether the reaction is in a state of dynamic equilibrium, or whether it goes essentially to completion.
The normal way we decide when any chemical reaction has reached its end point (and this applies to both cases mentioned above) is when the macroscopic properties of the system are no longer changing.

 

[wizzkids]

So if i put the reaction of CaCO₃ and HCl

That reaction has a very large enthalpy change and it will go essentially to completion. You could monitor the volume of gas released from the reaction and when it is no longer increasing then the reaction has reached its end point. Note that the total mass of the system will stay constant (provided it is a closed system and there are no leaks).

 

[Shavi Masee]

WOAHHHh thank you so muchh

That reaction has a very large enthalpy change and it will go essentially to completion. You could monitor the volume of gas released from the reaction and when it is no longer increasing then the reaction has reached its end point. Note that the total mass of the system will stay constant (provided it is a closed system and there are no leaks).

We ended up monitoring the gas! But instead of waiting for the complete reaction to occur, because we're measuring the rate of reaction we just waited till co2 reached a certain volume.

 

[C2H6O]

^^

depends on the reaction, but purely quantitative methods i can think of are
- if it produces a gas wait for the mass to change like you mentioned
- alternatively collect the gas in a graduated cylinder filled with water and use the volume to find the amount of moles
- if the reaction has ph changes use a ph probe to monitor the ph, then when the ph tapers off to a constant you know the reaction is complete
- if the reaction has a measurable change in enthalpy use a temperature probe and similar to ph wait for it to taper off
- use a colourimeter (you probably havent learned this yet but basically it calculates concentration based on the colour/darkness of a solution) to find the concentration and wait for it to taper off like before or see if it matches the expected concentration

 

[Shavi Masee]

depends on the reaction, but purely quantitative methods i can think of are
- if it produces a gas wait for the mass to change like you mentioned
- alternatively collect the gas in a graduated cylinder filled with water and use the volume to find the amount of moles
- if the reaction has ph changes use a ph probe to monitor the ph, then when the ph tapers off to a constant you know the reaction is complete
- if the reaction has a measurable change in enthalpy use a temperature probe and similar to ph wait for it to taper off
- use a colourimeter (you probably havent learned this yet but basically it calculates concentration based on the colour/darkness of a solution) to find the concentration and wait for it to taper off like before or see if it matches the expected concentration

OOOHH THANK UU ETHANOLL

We ended up doing the second one that u mentioned. But we had a controlled volume for the gas to reach before stopping the timer

The other group members didn't wanna do the mass one... we all thought that it wouldn't work out in the end.
Idk what enthalpy is yet
And I do know what colorimetry is (how it works ig), however our reaction didn't produce a colour.

 

[Study to success]

These words sound like gibberish to me lol

 

[Shavi Masee]

These words sound like gibberish to me lol

frfr still does to me

 

[C2H6O]

Idk what enthalpy is yet

oh lmao its really dumb it literally just means heat

 

[Shavi Masee]

oh lmao its really dumb it literally just means heat

all our tests were so bad, we have to re-do the entire experiment tmr T-T

 

[C2H6O]

wait actually thats oversimplified, its just the energy stored in the bonds of the substances, and adding more energy takes heat from the environment, while loosing energy will release it as heat into the environment, so you can measure it by measuring the temperature change of the solution