 Okay, so good evening everyone, good morning or whatever time you're watching this video right now. So I'll just make a quick reminder on how to compute the concentration of the unknown. So take for example, you did your measuring already using your spectrophotometer. So what you're going to get out of the spectro is actually your what? Your absorbance, okay? Your absorbance and according to Beerslaw, okay di ba? According to Beerslaw that your absorbance is equal to your concentration. So that is what we're going to calculate for this video. So the formula is actually the concentration of the unknown, your CU. So let me write it down for you first. All over AS times the CS. So what are these values all about? So the CU is actually the concentration of the unknown, okay? This is the concentration of the unknown, the concentration of your specimen or your sample. The CS, this is the concentration of your standard, okay? The concentration of your standard and this is actually most of the time known. So this is known or this is given, okay? This is given. So what about the AU and the AS? The AU and the AS is actually being measured using your spectrophotometer. So these two are the absorbance, okay? So this one now is the absorbance of the unknown, okay? Absorbance of the unknown or the specimen you're currently measuring. And this in turn is the absorbance of the standard, okay? Absorbance of the standard. So take for example, I measured, okay? Take for example, I have a given. So take for example, I know that the concentration of the standard is already 80 millimoles per liter, okay? 80 millimoles per liter. So I have that on me already. And what I'm going to have is the absorbance of the unknown and the absorbance of the standard. And how am I going to get this? I'm going to get this by measuring it in the spectrophotometer. So take for example, the absorbance of your unknown is actually 0.561. And then the absorbance of your standard is actually 0.978, okay? 978. So simple formula what you're going to do is to actually substitute the given. So the concentration of the unknown is equal to what? Absorbance of the unknown which is 0.561. All over 9, 0.978. Multiply it now by 80 millimoles per liter. So just do the math, okay? Just do the math with 0.561 divided by 0.978 times, okay? Times 80. That is actually what? 45.89 millimoles per liter. That is now the concentration of your unknown, okay? So we got the concentration of your unknown. This 45.78. I hope this would help you. So thank you. And see you on my next video. Bye.