This video series has been so helpful to me and given me more confidence to tackle the MCAT. Thank you so much for making this video series

@Leah4sciMCAT

4 жыл бұрын

You are so welcome!

(1) 4.19+ 0.15=4.33 (Always add constant of 0.15 to your pKa value) (2) 5.00-4.33=0.67 (increase the given pKa to the whole next number and subtract from that whole number answer you get from step 1) (3) 0.67 x10 = 6.7 (always multiply whatever number you get by 10) (4) 10^-5 ( one thing to note your 10^- number will be alway one digit higher than given pKa value) (5) 6.7x10^-5 Hope it helps everybody. Calc: 6.46x10^-5 .

@ghostmedic86

4 жыл бұрын

This works great unless the number is like 3.82.

@MsPslater

2 жыл бұрын

@@ghostmedic86 I found this method only works on negative numbers such as 10^-4.22 but like 10^3.86 it doesn't work, not sure why.

@Leah4sciMCAT

7 ай бұрын

I came up with a much simpler method recently, see my newer Logs video for the simpler shortcut

@alexanderpineschi3222

6 ай бұрын

​@Leah4sciMCAT hi I'm looking for this new simpler way but I'm not seeing any recent log videos can u maybe attach a link???

@alexanderpineschi3222

6 ай бұрын

​@@Leah4sciMCATkzread.info/dash/bejne/gqJoxdJmkczFc5s.htmlsi=HDYUb15mc6j-_IHp Is this it?

You are the best online teacher I ever known.Thank you.You really helped me

@Leah4sciMCAT

9 жыл бұрын

lirim sopaj thank you

Your videos are amazing, what a huge help. Thank you Leah :)

@Leah4sciMCAT

7 жыл бұрын

Glad you like them! You're welcome!

At 4:15 mark I believe you misspoke when you said "point 1 gives me an 8 and point 5 gives me a 5". I think you meant to say "point 1 gives me an 8 and point 3 gives me a 5". Due to the fact that you rounded 4.19 to 4.2 and (.2) lies half way between (.1) and (.3), which would then give the (8 x 10^-x) and (5 x 10^-x) values you use later in the problem.

@thenightdances21

2 жыл бұрын

yes, @Leah4sci can you confirm this because I'm struggling at this point to understand if you misspoke and how you got the final answer?

@Leah4sciMCAT

6 ай бұрын

Yes, thanks for catching that. I misspoke, it should be between 0.1 gives me 8 and 0.3 gives m 5

Omg i got so confused , your previous video was clearer...

@Leah4sciMCAT

9 жыл бұрын

Ricky Kalendarov what did you find confusing?

@bownic12

6 жыл бұрын

I have the same question!

@cmhardin37

5 жыл бұрын

I thought it was Crystal clear...

@Mahdi25009

4 ай бұрын

same

Thank you seriously so much. This was unbelievably helpful

@Leah4sciMCAT

6 жыл бұрын

You're very welcome!

Thank you, this was so helpful!

@Leah4sciMCAT

4 жыл бұрын

I'm so glad!

this is amazing for gamsat prep!!

@Leah4sciMCAT

7 жыл бұрын

thank you! glad to help Good luck on the GAMSAT

NICCCEEEE !!! Thank you.

@Leah4sciMCAT

5 жыл бұрын

You're welcome!

Basically what people are asking (I think), and which I'm also a little confused by, is at 4:27 where the answer is somewhere between 5x10^5 - 8x10^-5. I would have reasoned the range to instead be 5x10^4 - 8x10^4. I know this isn't right, but I don't see a logic behind why you chose the former (and correct) answer.

@Leah4sciMCAT

8 жыл бұрын

+Alexandra Anne Did you see my math cheat sheet on the values to memorize?

Leah4sciMCAT Hi Leah! I love your videos! I was a bit confused in this video around 4:04. You didn't mention how you determined that the exponent is going to be -5 and not -4 or some other number. Thanks!

@Leah4sciMCAT

9 жыл бұрын

I show you to round it

@hp8309

6 жыл бұрын

I just figured out why. We have to refer to the video before this one to see why. In the previous video, she says for -log ( 1 E -4), the pH has to be between 3 &4. That is, for any pH= - log (1 x 10 ^ -#) , the pH must be between (# - 1) & the #. So if we have pH = - log ( 1 x 10 ^ -7), the pH would be between 6 and 7. If we have pH = - log (1x 10^-5), the pH would be between 4 & 5 etc etc. Now, back to your question: 1. In the current video we know the pKa (or pH) is between 4 & 5 because 4.19 is between 4 & 5. 2. We pick the # (the exponent on Ka= y x 10^-#) to have a value of -5 because if we picked -4, the pH would have to be between 3 & 4, not 4&5 like we need. Remember earlier how I said for any pH= - log (1 x 10 ^ -#) , the pH must be between (# - 1) & the #. 3. At this point, we know our Ka has to end with 10^-5. Next, we can figure out what the coefficient in front of the x10^-5 is. 4. Next, we use the fact that 4.19 --> 4.2 and 4.1

@biancarosas409

6 жыл бұрын

@heli god bless you this helped me so much

@briana6547

5 жыл бұрын

oh thank you i just saw this after i commented lol

@therealreels1121

5 жыл бұрын

@@hp8309 you are a goddess!!! thank you!

Nice vedio it really help me thanks a lot

@Leah4sciMCAT

4 жыл бұрын

You're welcome!

is nice this tips improve my math

@Leah4sciMCAT

7 ай бұрын

Glad it was helpful to you!

Great video. May I recommend, for continuity with the previous video (MCAT Math Vid 8,) that at 3:40 you flip the table? i.e. in the previous video, the "#.1" was on the bottom, though in this video, it is on the top. That made this video a bit more challenging to follow (since I just watched the previous before this.) Thank you again for all of your help.

@Leah4sciMCAT

10 жыл бұрын

Alas KZread does not allow video editing

@bgeer8452

10 жыл бұрын

I understand. All the same, very helpful information. I find the videos very helpful for visual learning, and the commentary helps reinforce the concepts. Great stuff!

This wasn't as clear, I got lost once we got to the 10^-4.19=Ka. I wasn't sure what was happening. I have rewatched taken notes over and over. :(

@israelsanchez1225

3 жыл бұрын

Watch the previous video multiple times and very carefully to understand the trick. Its basically the trick from the first video in reverse.

@Leah4sciMCAT

3 жыл бұрын

I’m sorry there has been some confusion with this concept. The idea is that a pKa of 4.19 lies between the whole numbers 4 and 5. Since Ka = 10^-pKa, the Ka for this acid must fall between 10^-5 and 10^-4. If only one of your MCAT answer choices falls within that range, that’s great! You’ve got your answer. If not, it can be helpful to memorize a set of decimal values that give slight variations in your answers to anti-log calculations. Thanks for commenting!

I analyzed this video for well over an hour and I'm still lost in the sauce

@Leah4sciMCAT

11 ай бұрын

Say what?

Hi Leah, I really like your video very much and they help a lot! But I just have one question toward the end of the video: isn't 6.46 x 10^-5 actually closer to 5 x 10^-5 instead of closer to 8 x 10^-5 (I think you said it's closer to 8 x 10^-5)? In this case if there are 2 answer choices between 5 x 10^-5 and 8 x 10^-5 how do I know which one it is?

@Leah4sciMCAT

9 жыл бұрын

Alice Liou if you take the midpoint between 5 and 8 you get 6.5 which means that yes, you are correct. Can't believe I missed this ;) That being said, the MCAT is not out to trick you. The topics/passages are difficult but the answers are straight forward if/when you have the right background and setup. They won't trick you like this

Will you be rerecording this soon? The video is mostly helpful but there are some areas where I have trouble following due to speed. Thanks!

@Leah4sciMCAT

2 жыл бұрын

I don't have plans to re-record. Have you gone to settings to change it to a slower speed when I talk too fast for you?

I think what people are confused is to why the -4 wasnt selected and why -5 was. Yes its because the pH would of have to been 3.19 but how can we calculate to know that? And eliminate -4.

@Leah4sciMCAT

5 жыл бұрын

At which point of the video please?

Leah 3:58 please explain why you chose 8 x 10^-5 instead of 8x 10^-4. I watched all the other videos in this series and took notes based on your videos, but I don't understand why you chose -5 instead of -4.

@Leah4sciMCAT

5 жыл бұрын

Since 4.19 is between 4 and 5 we have to look at both.

im confused on why it is to the -5th power not -4th

@Leah4sciMCAT

9 жыл бұрын

Jennifer Buraga which part?

@Sunshine-vt7kh

3 жыл бұрын

@@Leah4sciMCAT I would also like to know this! It confused me too. Around your 4 minute time stamp, how did you know your answer was going to be to the -5th power instead of the -4th power?

Goes a little off the rails in the second half.

@Leah4sciMCAT

6 жыл бұрын

Thanks for the feedback

I realize this question has been asked before, but I don't think you gave a satisfactory answer. Since our desired number has the exponent lying between 4 and 5, why did you pick 5 instead of 4 as the exponent? In other words, why didn't you pick our value ranges to be between: 5 x 10^-4 and 8 x 10^-4? How did you know to go with -5 instead of -4 as the exponent?

@Leah4sciMCAT

9 жыл бұрын

pkibera which part of the video are you asking about? I don't really understand your question

@Leah4sciMCAT

9 жыл бұрын

Leah4sciMCAT I just rewatched the video and found your question. 8x10^-4 is between 1x10^-3 and 1x10^-4. But since we have 4.19 and not 3.19 we can't use the range of 3-4

Your videos have been very helpful, thank you! Can you help me understand how you decided that the x exponent would equal 5 at 3:53. Please advise, thanks!!

@Leah4sciMCAT

9 жыл бұрын

Nathalie S 4.19 is between 4 and 5

@lavarwilliams3284

9 жыл бұрын

Leah4sciMCAT I get that but 4.19 is closer to 4 than it is to 5 so it seems like the exponent would be 4

Hello, how can I approximate 1x10^-5.4 or any 10 to a negative decimal? the answer is 3.9 x10^-6 but how?

@Leah4sciMCAT

8 жыл бұрын

+Dana Kar You have to approximate using the 2 closest whole number values. 1x10^-5 and 1x10^-6

at 4:45, you said the answer was between 5 x 10^-5 and 8 x 10^-5; why is it raised to negative 5 and not negative four? other people asked this question below but you do not provide an explanation as to why?? In the video before this one, i thought i had to stay in the range you give us, therefore between negative 4 and negative 5 exponents.

@Leah4sciMCAT

3 жыл бұрын

Sorry for the late reply. You must remember that a number raised to the power of -5 is smaller than a number raised to the power of -4. Therefore, the range we must stay in for this problem is between 1 x 10^-5 (smaller) and 1 x 10^-4 (larger). If I were to say my answer is between 5 x 10^-4 and 8 x 10^-4, I would be exceeding my expected range. Both of those values are greater than 1 x 10^-4.

Hello, love your videos, but I am very confused. I get up to the point where the Ka is in the range between 1x10^-4 and 1x10^-5 and am confused with the final answer you get. Isn't 6.46x10^-5 larger than 1x10^-5 therefore being out of the range??

@Leah4sciMCAT

8 жыл бұрын

+Andrew Dunn I challenge you to turn each of these numbers into a decimal and compare

@andrewdunn777

8 жыл бұрын

6.46x10^-5 = 0.0000646. 1x10^-5 = 0.00001. To me it still looks like the 6 is larger and therfore not in the range. I know I must be wrong, but cannot see how.

Hi Leah. I understood up until around the 3:40 minute mark. I think I’m confused on the exponent x part & how the answer came out to be around 5 & 8. Can you please clarify & explain?

@Leah4sciMCAT

11 ай бұрын

The pKa of 4.19 is somewhere between 4.1 and 4.3. Based on the numbers in green that I ask my students to memorize, that puts our Ka value somewhere between 5 x 10^-5 and 8 x 10^-5. To understand more about how I got these values to memorize or why they are important for logarithmic calculations, make sure to watch my full MCAT math tutorial at Leah4sci.com/MCATmath or download the accompanying cheat sheet at leah4sci.com/mcat-math-study-guide-cheat-sheet/

this video is very confusing last one is very clear kindly explain once again please

@Leah4sciMCAT

7 жыл бұрын

I'm sorry that you're finding this video confusing. I'm Thinking of redoing this topic but not anytime soon. Please see if other youtubers have posted similar explanations so that you can find another explanation quickly

i understood the first part now am confused how to calculate negative log of 5,7 or any decimal am not able to fig out please explain

@Leah4sciMCAT

6 жыл бұрын

At which point in the video?

Hi Leah, why did you end up going for 10^-5 for the pH= 4.19 problem? We had two options of 10^-4 and 10^-5 when you explained that we need to round down and up to 4 and 5, respectively. but it wasn't explained why -5 was a better answer choice. Why did we go for 5?

@FreakishWolf

5 жыл бұрын

-4 would give the value of 4.0 while -5 would give any of the values between 4 and 5. 10^-4 is 10 x 10^-5 and results in the 4 value, 8 x 10^-5 gives 4.1, 5 x 10^-5 gives 4.3, 1 x 10^-5 gives 5

@stephaniecantu6973

5 жыл бұрын

How would you find this out by hand? @@FreakishWolf

@TheSab003

5 жыл бұрын

@@FreakishWolf Thank you so much! Got it.

@Leah4sciMCAT

7 ай бұрын

10^-4 is 10x bigger than 10^-5, so if you're choosing a number between 1 and 10, you have to keep this in mind. That being said, I realize that this method is quite confusing and have since come up with a MUCH easier shortcut that I teach in my newer logs video. You can find it here: leah4sci.com/mcatmath

why did you go with the ^-5 and not ^-4?

@Leah4sciMCAT

5 жыл бұрын

At which specific point in the video?

nice. Its really helpful for my future MCAT exam.

@Leah4sciMCAT

10 жыл бұрын

awesome, when are you testing?

@bbazarov176

10 жыл бұрын

Leah4sciMCAT I wish I could take it now, but I have not finished my undergraduate yet. Probably I am going to take it in 2-3 years, and definitely gonna use your tutorials. Thank you so much. Glad that I found these videos. I will use your videos to survive my CHEM classes.

@Leah4sciMCAT

10 жыл бұрын

Wow 2-3 years is quite a ways away. Are you currently a Freshman or Sophomore?

@bbazarov176

10 жыл бұрын

Yeah I know. I have quite a lot of time, and I am freshman. Just finished my 2nd semester.

@Leah4sciMCAT

10 жыл бұрын

Haha no worries then. Right now focus on getting good grades, keeping your GPA high, and building a strong foundation. There will be a new MCAT format by the time you test.

how did u round to X10^-5 .... ????? 4.19 is closer to X10^-4

@Leah4sciMCAT

9 жыл бұрын

Sibin Mathews you have to round up AND down to find the in between

where is you video on buffers?

@Leah4sciMCAT

10 жыл бұрын

non-existent at this time, however I will be happy to teach you this information via private tutoring session. Details on my website leah4sci.com/mcat-tutoring

You have a soothing voice, you should do narrating

@Leah4sciMCAT

3 ай бұрын

Thank you, I appreciate your kind words. Hope you found this video helpful

I am confused how we are sure that the exponent will be 10^-5 and not 10^-4 (3:53)

@Leah4sciMCAT

4 ай бұрын

Since the starting value is 4.19, it is already larger than 4. So we must upgrade our exponent to the more negative number of -5. Just to check, you could do the -log of 8x10^-4 in your calculator and find that it would give us around 3.1 (smaller than our original value) while doing the -log of 8x10^-4 gives us 4.1.

@nikkinyarko

4 ай бұрын

@@Leah4sciMCAT Makes sense, thank you!

Log has never been this easy for me

@Leah4sciMCAT

5 жыл бұрын

Glad I could help!

Get the gist thanks, just got confusing at the end

@Leah4sciMCAT

6 жыл бұрын

You're welcome! What was confusing about it?

why 10^-5???

@Leah4sciMCAT

7 ай бұрын

I'm sorry, but I don't understand the context of your question. If you have a question about the example in this video, please contact me through my website at Leah4sci.com/contact and provide a time stamp along with any additional comments and/or questions.

GOAT

@Leah4sciMCAT

2 жыл бұрын

Thanks!

Same question Jennifer, Natalie, and meowismeify asked below. You do not explain how you arrived at the exponent 5 instead of 4. I'm not sure how else to ask the question. What part of my questions don't you understand? The desired value lies between two exponents (4 and 5), and you picked 5. However, you do not provide a rationale for why you picked 5 instead of 4 or why you did not pick 4. As mentioned. the same question has been asked by 3 other people, but you haven't yet answered the question.

@Leah4sciMCAT

9 жыл бұрын

pkibera As explained in the video, if the value is between 4 and 5 you have a number between 1x10^-4 and 1x10^-5. the first is the same as saying 10x10^-5 and so we choose a number between 1 and 10, and put that to the exponent of -5

Confusing.

@Leah4sciMCAT

5 жыл бұрын

What specifically about the video was confusing? I'm always looking for feedback to help me improve future videos.

Hey Leah, I think you should delete this video and remake an updated version to cover some important points that you might have left out

@Leah4sciMCAT

6 жыл бұрын

I appreciate your feedback, but what do you think I left out?

This video got confusing after 5:02

@Leah4sciMCAT

6 жыл бұрын

Thank you for the feedback, but I'm confused. That's just where I tell you where you can find additional resources.

@hp8309

6 жыл бұрын

she picks the -5 because if she picked -4, the pH would be between 3 & 4, not 4 & 5 like we discovered earlier on in this video.

@stephaniecantu6973

5 жыл бұрын

How do you figure that out @@hp8309