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Interesting Chemistry Things

Nymphetamine

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A 25.00mL sample of HCL solution requires 43.50mL of 0.502M Ba(OH)2 for neutralization. What is the concentration of the HCl solution?

2HCL + Ba(OH)2 ---> BaCl2 + 2H20

GOGOGOGOGOGGOGO!
 

winston53660

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A 25.00mL sample of HCL solution requires 43.50mL of 0.502M Ba(OH)2 for neutralization. What is the concentration of the HCl solution?

2HCL + Ba(OH)2 ---> BaCl2 + 2H20

GOGOGOGOGOGGOGO!
Huh????????????
 
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A 25.00mL sample of HCL solution requires 43.50mL of 0.502M Ba(OH)2 for neutralization. What is the concentration of the HCl solution?

2HCL + Ba(OH)2 ---> BaCl2 + 2H20

GOGOGOGOGOGGOGO!
1.75 M

Here is a simple organic synthesis:



Fill in the steps.
 
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Chemistry problems I'm trying to get answered before the mods move this to the sewer.

Na (s) + 1/2Cl2 (g) ---> NaCl (s)

Predict the sign of entropy, + or -
-

You are going from two species, one being a gas, to a solid. The left hand side has more disorder than the right.
 
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iangb

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A 25.00mL sample of HCL solution requires 43.50mL of 0.502M Ba(OH)2 for neutralization. What is the concentration of the HCl solution?

2HCL + Ba(OH)2 ---> BaCl2 + 2H20

GOGOGOGOGOGGOGO!
To neutralise, you need half the moles of barium hydroxide as you do of the hydrochloric acid. To put that mathematically:
no. moles HCl = (0.5) x no. moles Ba(OH)2

Using the all-purpose equation:
no. of moles = volume x concentration

you get:
43.5 x 0.502 = (0.5) x 25 x [conc. of HCl].

You can do the maths bit.

Na (s) + 1/2Cl2 (g) ---> NaCl (s)

Predict the sign of entropy, + or -
Not a question I'm so familiar with. My guess would be; gaseous chlorine is becoming a solid. What must that be doing to the entropy of the situation? However, there are lots of potential answers.

...next time, do your own homework :2razz:

EDIT: Ach, beaten to it!
 
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marduc

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we first need to know how many molecules of Ba(OH)2 are in the 43.5 ml solution

I will try to go step by step here

.502 M = .502 moles / liter of Ba(OH)2.

lets convert 43.5 ml to liters so we have the same unit across the board.

43.5 ml * 1liter / 1000 ml = .0435 liters

ok so next how many moles of Ba(OH)2 in the sample:

.502 moles / 1liter * .0435 liters = 0.0218 moles Ba(OH)2

Now looking at your reaction:

2HCl + Ba(OH)2 ---> other stuff

we see that for every unit of Ba(OH)2 we need 2 units of HCL since the unit is moles, then we need 0.0218 * 2 moles of HCl

0.0218 * 2 = 0.0436 moles of HCL

ok getting close we now know that there are 0.436 moles of HCl in the 25.00 ml sample, just need to convert that into moles per liter and you are set.

and since I am taking this step by step, lets convert ml to liters first just to get that out of the way

25.00 ml * 1 liter / 1000 ml = .02500 liters

so we now have (pay heed to sig figs.. because your teach will nitpick on them):

0.0436 moles / .0250 liters = x moles / liter

0.0436 moles / .0250 liters = 1.744 moles / liter or 1.74 M


* make sure to check my work for silly errors like a miscalculation, or typing a wrong digit or omitting one, i was more concerned with outlining the steps than being fastidiously accurate. also don't forget the sig figs, im sure your teacher will harp on those, and there is a sig fig discrepancy built into that problem..

edit: I got beat too , but I took the extreme scenic route to try to show you in detail how to solve it. and did i screw up I see someone else with a diff answer def. check the work. it has been a LONG while since i worked this stuff
 
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iangb

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We both got beat - but we got the right answer. I'm not sure how helter got theirs - but mine and yours match.

EDIT: speaking of helter's mistakes; if disorder is decreasing, surely the sign of entropy would be -, not +?
 
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We both got beat - but we got the right answer. I'm not sure how helter got theirs - but mine and yours match.

EDIT: speaking of helter's mistakes; if disorder is decreasing, surely the sign of entropy would be -, not +?
Good call, I had it backwards. An increase in entropy is an increase in disorder.
 

Nymphetamine

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Thank you thank you thank you thank you thank you
 

spud_meister

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dear god, the only thing i learnt in chem was that Mol's aren't always fuzzy little digging creatures, and not to drop rubidium into a beaker full of water.
 

iangb

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dear god, the only thing i learnt in chem was that Mol's aren't always fuzzy little digging creatures, and not to drop rubidium into a beaker full of water.
The 'alkali metals + water' demo remains one of the coolest bits of chemistry that I get to teach. Until I can persuade our lab tech to build us a Rubens tube, that is.
 

Lord Tammerlain

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The 'alkali metals + water' demo remains one of the coolest bits of chemistry that I get to teach. Until I can persuade our lab tech to build us a Rubens tube, that is.
Sulphuric Acid and sugar is a good one as well
 

Lord Tammerlain

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Is that the one where the sugar bursts into flame?
No

If done in a graduated cylinder it will act more like a carbon snake (aka south Park)

Thermite is also an interesting chemical reaction
 

spud_meister

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The 'alkali metals + water' demo remains one of the coolest bits of chemistry that I get to teach. Until I can persuade our lab tech to build us a Rubens tube, that is.
see, i didn't get so much taught it, as the teacher foolishly gave me a piece of rubidium to have a look at, 'cause i had to write a short essay about it, and i 'accidentally' dropped it in a beaker:mrgreen:
 
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