Відео

Yes, the horizontal center. That's the easiest way to remember.

To find the concentration in mg/L, you will want to convert 0.004 mol to g using the n = m/M formula (solve for m which is mass in grams), then convert grams to mg by multiplying by 1000. 🙂

Glad it helped!

Glad to hear it Yuvaraj!

Great observation! But the volume of the drops is insignificant when compared to the volume of water in the flask below.

@@pennymarcotte thanks for the quick reply, I always wondered about that!

how to did you get the mass of solute?

@@lyannapadillo991 Hi Lyanna - there are two general steps to finding the mass of solute needed to make the stock solution: 1) calculate the number of moles required to make 0.100 L of a 0.250 mol/L solution: V = 0.100L C = 0.250 mol/L n = ? Rearrange C=n/V to n = C×V, then substitute in the values above: n = (0.100L)(0.250mol/L) n = 0.0250 mol Therefore 0.0250 mol are required to make the stock solution. 2) Find the mass of copper(II) sulphate pentahydrate (CuSO4•5H2O) needed to make the solution: n = 0.0250 mol (from Step 1) M = 249.72 g/mol (from periodic table) m = mass? Rearrange n = m/M to isolate m: m = n × M m = (0.0250 mol)(249.72 g/mol) m = 6.243 g m = 6.24 g (to 3 significant digits) Hope this makes sense!

@@pennymarcotte How can I prepare 1.25 M sugar solution diluted to 1 L?

@@lyannapadillo991 you can use the process I've outlined above, except your concentration is 1.25 mol/L and you need to prepare 1L. 1) find the number of moles required using n = C×V 2) find the mass required using the moles found in Step 1 and the molar mass (M) of sugar (C12H22O11) n = M = m =? m = n × M

Thanks for the feedback Elliott!

Hope it helps! I must say I'm relieved we had some if these videos prepared before covid. Wishing you and your students the best of luck this year!

Penny Marcotte 7 years ago and your still responding 😭

Which calculation did you need some extra assistance with?

@@pennymarcotte I'm need to make a liter of a 0.1 M HCl from a stock. So I need to know what volume of water and HCl I need to add for that.

@@Samuitsuki so are you clear on how to use the C1V1=C2V2 formula to find the amount of stock required? C1 is the original stock concentration, C2 is the desired concentration (0.1M), and V2 is the final volume you need (1L). Then you will solve for V1. Not sure what your stock concentration is, but your rearranged formula will look like this: V1 = (C2 x V2)/C1 Once you know how much stock you need, then you can determine how much water needs to be added to top it up to 1L. Hope this helps!

@@pennymarcotte Thanks for the quick reply.

@@Samuitsuki good luck with your calculations

@Divine Brawl Stars *3

because it goes up by 0.2 and there's three lines instead of it being 0.1,0.2,0.3, it will be 0.2,0.4,0.6 so it will be 7.6

If I could speak Hindu, I would!

Plus in a very short amount of time!

Well thank you! I have to say I never expected anyone beyond my own class would see this. Glad it's been useful to some of you.