14.1 Rates and Rate Expressions

[@Morganwmahan]

This helped me more than you know. Simple, Clear, Concise. Teachers should strive to master the skills you have. Unfortunately most teachers are overly concerned with students perception of themselves and complicate a simple subject trying to display themselves as smart.

[@thesn0wcone]

chads a god sent, change my mind.

[@leticiaaguirre8126]

you took the words right out of my mouth

[@ChristianSpencer-c9g]

agreed

[@cardiacmyxoma4073]

Hi Chad, I just wanted you to know that I scored a 517 on my MCAT with a 131 on the chem/phys section. I 100% believe that it's due to your videos. They've been a great help. Thank you so much for all you do!

[@ChadsPrep]

Nice work, Situs - glad to hear you scored so well! Thanks for letting us know!

[@monpetitgarcon]

@cardiac myxoma lol I am anxiously preparing to sit for mine and I am very happy to discover Chad's channel for my prep!

[@حليمهالحربي-د7ض]

@@monpetitgarconش

[@emmafisher8033]

Thank you so much for all of your videos! You have taught me exponentially more than my current professor.

[@ChadsPrep]

You're very welcome Emma! Glad you're finding them helpful!

[@meiyaoli2258]

So simple and clear that even I can understand, love your teaching style...

[@ChadsPrep]

Thank you very much! So glad you found this lesson helpful!

[@emilyeskiw2744]

I have one of the worst profs I have EVER had in my gen chem 2 course this year, I am not kidding when I say that these videos hands down saved me. Thank you so so much

[@ChadsPrep]

Glad the channel is helping you - Happy Studying!

[@abdinasirabdukadir9783]

Thank you teacher, you gave me great hand to get it easily coz have confused mi teachers' expressions thank you more from Somali.

[@ChadsPrep]

You're welcome!

[@mosokodimichellemawasha6191]

I am repeating my final year in bsc.. However i just came across your chanel today.hoping for great results😀 Will comeback and give an update pf how its going.

[@ChadsPrep]

Glad you found the channel - Happy Studying!

[@dani3002el]

Hey Chad, when calculating the rate of change of NH3 can you explain why it’s 8 & not 6? Why wouldn’t we just divide 12 by the coefficient of NH3?

[@jasonlan7475]

Not Chad but I think I got that part. For every 3 moles of H2 produced, it took 2 moles of NH3 (shown through the stoichiometry). For 12 moles of H2 to be produced, the reaction "occurred" 4 times (because 4 x 3 =12). Therefore 2 x 4 = 8 moles of NH3 is required.

[@Julian-tf8nj]

SUPERB teacher! Thanks 😀

[@ChadsPrep]

You're welcome, Julian - and thank you!

[@benjaminfranklin4149]

Are all states of species included in rate expressions? We know that solids and pure liquids are not included in the rate law for a reaction, but I'm not sure for rate expressions. Thank you!

[@ChadsPrep]

Be careful on this one Benjamin ;) Solids and liquids generally are not included in *equilibrium constant expressions* , but quite commonly appear in *rate laws* and *rate expressions* . Hope this helps!

[@benjaminfranklin4149]

@@ChadsPrep Very helpful. Thank you so much!

[@ChadsPrep]

@@benjaminfranklin4149You are welcome!

[@youngcoreana3760]

I wish he was my chemisty professor,,,

[@ChadsPrep]

Thanks for saying so.

[@williamcripfoe6754]

You have saved me, thanks so much

[@ChadsPrep]

You're welcome, William - Happy Studying!

[@alissa7760]

Why does the concentration go down? How do we know? I get how we have to put ”-” sign to make the answer positive but I just don't get why the answer would be negative if we don't put ”-” sign.. Please help, my chem teacher at school isn't very helpful lol

[@ChadsPrep]

It would work the same way with your bank account and may make a little more sense in that context. If you deposit money into your account that is a positive change reflecting the increase in money in your account, but if you spend or withdraw money from your account that is a negative change reflecting the decrease in money in your account. So, Increase = + change Decrease = - change You can also see this by simply calculating the change in concentration as "final - initial." For a product the final concentration is greater than the initial so the change in concentration comes out positive. But for a reactant the final concentration is smaller than the initial and so the change in concentration comes out negative. So rate is defined as change in concentration over change in time. For the reactant the change in concentration is negative as stated above so the rate would be negative as well. A proper rate expression gives the rate of the reaction in terms of any species in the reaction and the lords of chemistry decided that it should always be defined as being positive which is why we need to multiply the rates of reactants by -1. Hope this helps!

[@be.alrightx5386]

Be my teacher please

[@ChadsPrep]

If you're in AZ there's a chance, otherwise youtube and chadsprep.com will have to do! Best in your studies!