# Annoying Chemistry Question **URL:** \ **Category:** Factual Questions\ **Created:** [November 8, 2002, 4:38am UTC](https://boards.straightdope.com/t/annoying-chemistry-question/135841 "2002-11-08T04:38:22Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Civil\_Defense](https://avatars.discourse-cdn.com/v4/letter/c/ccd318/32.png) [@Civil\_Defense](https://boards.straightdope.com/u/Civil_Defense)\ **Post date:** [November 8, 2002, 4:38am UTC](https://boards.straightdope.com/t/annoying-chemistry-question/135841/1 "2002-11-08T04:38:22Z")
Apparently, my attempt to post was lost in a browser crash. So, let me try again 🙂 First, let me point out that I’m not asking anyone to do my homework for me. I would, however, be very very appreciative if someone could point me in the right direction-- or let me know what it is I’m doing wrong. Second, let me reiterate how much I hate Chemistry. As a non-Chem major, I loathe taking it but it’s apparently a required class here, no matter your major. That said… Okay, so given 50 mL of .5M HCl and 55 mL of .5M NaOH, we reacted them and are to determine how many moles of H2O formed as a result. So… I figure that I can use mole ratios to find out the H2O, right? 50 mL of HCl = ((1+35.5) / 50) = 1.367 moles 55 mL of NaOH = ((23+17) / 55) = 1.25 moles 1.367 HCl + 1.25 NaOH = 2.616 moles of H2O + NaCl, right? So, since the ratio of H2O to NaCl is .308 to 1, I can take .308 and multiply it by 2.616 moles to get .805 moles of H2O, right? If so, why is this program telling me that’s wrong? \>.\< Ugh… I’ll be glad when this semester is over, so I’ll never have to touch Chemistry ever again. I praise anyone who can offer any advice or direction… you will be honored. cd CompSci Major, Physics Minor ---
**Author:** ![antechinus](https://avatars.discourse-cdn.com/v4/letter/a/fbc32d/32.png) [@antechinus](https://boards.straightdope.com/u/antechinus)\ **Post date:** [November 8, 2002, 4:56am UTC](https://boards.straightdope.com/t/annoying-chemistry-question/135841/2 "2002-11-08T04:56:39Z")
> [@](#): > > \*Originally posted by Civil Defense \* > \*\*Apparently, my attempt to post was lost in a browser crash. So, let me try again 🙂 > > \ > > Okay, so given 50 mL of .5M HCl and 55 mL of .5M NaOH, we reacted them and are to determine how many moles of H2O formed as a result. So… I figure that I can use mole ratios to find out the H2O, right? > > 50 mL of HCl = ((1+35.5) / 50) = 1.367 moles > 55 mL of NaOH = ((23+17) / 55) = 1.25 moles > \*\* > When I went to school it was M=n/V. > Anyway you have excess NaOH (0.0275 moles) compared with HCl ( 0.025 moles). So use the moles of HCl to give an equivalent number of moles of H20 (0.025 moles). > \*\* > 1.367 HCl + 1.25 NaOH = 2.616 moles of H2O + NaCl, right? > [b/] > No. Dont add them. Use the ratio. 1 mole HCl gives 1 mole H2O. > \*\* > So, since the ratio of H2O to NaCl is .308 to 1, I can take .308 and multiply it by 2.616 moles to get .805 moles of H2O, right? If so, why is this program telling me that’s wrong? \>.\< > > Ugh… I’ll be glad when this semester is over, so I’ll never have to touch Chemistry ever again. I praise anyone who can offer any advice or direction… you will be honored. > > cd > CompSci Major, Physics Minor \*\* ---
**Author:** ![Civil\_Defense](https://avatars.discourse-cdn.com/v4/letter/c/ccd318/32.png) [@Civil\_Defense](https://boards.straightdope.com/u/Civil_Defense)\ **Post date:** [November 8, 2002, 5:01am UTC](https://boards.straightdope.com/t/annoying-chemistry-question/135841/3 "2002-11-08T05:01:14Z")
oh damn. That was so simple. You’re awesome… and quite fast. My chemistry grade thanks you. ---
**Author:** ![zigaretten](https://avatars.discourse-cdn.com/v4/letter/z/91b2a8/32.png) [@zigaretten](https://boards.straightdope.com/u/zigaretten)\ **Post date:** [November 8, 2002, 5:07am UTC](https://boards.straightdope.com/t/annoying-chemistry-question/135841/4 "2002-11-08T05:07:48Z")
No No No… 0.5M HCl means there are 0.5 moles of HCl per liter. (50ml) (0.5moles HCl/1000ml) = 0.025 moles of HCL (55ml) (0.5moles NaOH/1000ml) = 0.0275 moles NaOH So you have 0.025 moles of H+ and 0.025 moles of Cl- and 0.0275 moles of Na+ and 0.075 moles of OH-. For each H2O you need one H+ and one OH-. Since you have more OH- than you have H+, you will have some OH- left over. You can only make as much water as you have enough H+ for. So you will only get 0.025 moles of water.