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Calculate Volume of Solute in Percent Volume_Volume (% V_V) 002

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Okay so let's try this problem that says: a label on a 0.750 liter bottle of Italian wine indicates 11.5% alcohol by volume. How many milliliters of alcohol does the wine contain? Okay, the stuff that's given to you in the problem is up there (content on whiteboard). Let's assume that this 11.5% here is in 100 liters of the wine. Okay? That would make our lives a lot easier. Okay? So, if I've got 100 liters of wine, right, of 11.5 liters, of those (total) liters are going to be alcohol. Does everyone understand what I'm saying? Okay. So, we've got a conversion factor effectively from this here. That for every 11.5 liters of alcohol we have, we've got 100 - and I"m going to put a decimal place there - liters of wine. Okay, but not that big of a deal. So, what we can do is take this conversion factor, plug it up here, cross out or cancel out our liters of wine, the units, and we'll get liters of alcohol. And from that we can convert that to milliliters. Does everyone understand what I'm doing? Okay, so let's do that. So, instead of the volume of wine now, let's figure out well what is the volume of alcohol we're going to have? But this would be in liters right? We're going to get this in liters. So, 100 liters of wine on the bottom so we can cancel that out and 11.5 liters of alcohol on top. So when we do that, okay so (helping a student off screen) okay so when we do that, we get so 3 sig figs (significant figures), 3 sig figs, so this thing is going to have 3 sig figs goes 0.0862 - well this is ones that does that weird rounding behavior. Okay? So, 0.0862 because remember when it's only the 5 after it it goes always to the even number. So .0862 liters, right? So, to get milliliters out of that just 1, 2, 3 (move the decimal three points to the right) right. So, when we look at this it's going to be 86.2 milliliters of alcohol. Are there any questions on that one? So if you're having trouble that rounding rule, I saw some of you kind of cross your eyes, at that point in time, make sure you go back. It's that weird rounding rule, okay, so just make sure you go back if it's only 5 - if 5 is the last number - you have to round it to the even number. So that's why we didn't round it to 3, we kept it at 2.

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Duration: 3 minutes and 51 seconds
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Language: English
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Posted by: christineward on Sep 13, 2015

Calculate Volume of Solute in Percent Volume_Volume (% V_V) 002

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