Runner

Thank you for the reply. The reason why I’m asking this is because I have to plan an experiment to suggest that the enthalpy change between a metal and a solution of a salt is related to the relative position of two metals in the reactivity series. Firstly I thought that if the reaction takes too long I should use a temperature –time graph and use a temperature correction method to obtain an accurate result. If the reaction is slower than a neutralisation reaction I could simply just note the maximum temp it reaches. Which one is most sensible If I was going to use about 3.30g of zinc with the solutions being approximately 50cm^3 ? Thank you.

Can anyone please tell me how fast these reactions will occur. Haven't done the experiments yet, so I'm mystified Zn(s) + CuSO4(aq) ==> ZnSO4(aq) + Cu(s) Zn(s) + Pb(NO3)2 (aq) ==> Zn(NO3)2 + Pb(s) Any help would be much appreciated. Thank you.

Ahh ... So if I find the mass of the saturated Ca(OH)2 to be 0.3g and I originally added 0.5g to 0.1 dm^3. The solubility would be 0.3g x 1 dm^3/0.1 dm^3 ?

Thanks for the reply. What I can duduct is that there is a method of calculating the solubility by determining the Ksp, although I have no idea how to do that . Also, will the solubility be in g dm^-3 . Unfortunatelly my teacher told me that the titration will have to be done with HCl, he also told me that I have to calculate a reasonable concentration of HCl that needs to be used in the titration. The only way I can think of calculating is by trial and improvement. So it doesn't matter what mass of Ca(OH)2(s) I use in the experiment? Thanks again

Greetings, I was wondering if someone could help me with some of my chemistry difficulty. I have to do an experiment to find the solubility of calcium hydroxide. I have gone as far as to prepare the saturated solution of calcium hydroxide and to plan a titration with HCl. My problem is that I do not know what concentration of HCl I should use, how would I calculate a reasonable amount? Also, correct me if this is wrong. If I measure out 0.5g of calcium hydroxide dissolve it in water, filter it through a funnel and then titrate the saturated solution, I will be able to compare it with the original mass I measure out. To compare the solubility would I just say the mass of calcium hydroxide that was not saturated is evidence to suggest that it is sparingly soluble? Or is there a standard method of doing this? Please, any help would be much appreciated. Thank you in advance.

Sorry I can’t answer your question, but I have on myself. Did you get the Americium from a smoke detector?

Does anyone know what the melting point of pyrex glassware is?

If only I can comprehend, but interesting nonetheless.

Oops, didn’t realise the melting point of NaCl is 800C

Only if I use NaCl dissolved in water, I’ll be using molten NaCl.

That won’t be much fun will it? Another benefit of making HCl out of NaCl is that I get pure Na as a by-product, which also has its uses. My main problem now is setting up a contraption for this.

LOL .... Vomiting would probably be the easiest way to obtain it, I just think it will take a hell of a lot of vomiting and also it wouldn’t be as pure as what is needed. I thought perhaps electrolysis with molten NaCl. The problem is setting up the apparatus, I know if I spilt the ions by means of electrolysis, Cl2 will be given of which could then react with H2O, I think, giving me HCl. Don’t know if this will work though.

Can anyone give me some help on how I could effectively and efficiently make HCl ? Any help would be greatly appreciated, thank you.

Good try. I manage to work it out after spending almost 10 hours on it. (i) MgO + 2HCl ==> MgCl2 + 2H2O (ii) NaOH + HCl ==> NaCl + H2O moles of hydrochloric acid added to the magnesium oxide = 100 ÷ 1000 x 2 = 0.20 mol HCl moles of excess hydrochloric acid titrated = 19.7 ÷ 1000 x 0.2 = 0.00394 mol HCl (mole ratio NaOH:HCl is 1:1 from equation (ii)) moles of hydrochloric acid reacting with the magnesium oxide = 0.20 - 0.00394 = 0.196 mole MgO reacted = 0.196 ÷ 2 = 0.098 (1: 2 in equation (i)), the formula mass of MgO = 40.3, so mass of MgO reacting with acid = 0.098 x 40.3 = 3.95g, % purity = 3.95 ÷ 4.06 x 100 = 97.3%

Local anaesthetic drugs act by causing a reversible block to conduction along nerve fibres.

You would not be able to say neither 12:00 am nor 12:00 pm as it would be exactly from that point we measure from, however, when it is a second past the 12:00 mark it would turn into 12:00 am. You can definitely not say 12 pm because the pm indicates that it is before twelve.

Could someone please help, these calculations are driving me insane. BTW, this has nothing to do with calculating the empirical formula, I thought it would have been a waste of space if I had started a new thread. Here goes... Magnesium oxide is not very soluble in water, and is difficult to titrate directly. Its purity can be determined by use of a 'back titration' method. 4.06g of impure magnesium oxide was completely dissolved in 100cm^3 of hydrochloric acid, of concentration 2.0mol/dm^3 (in excess). The acid required 19.7cm^3 of sodium hydroxide (0.20mol/dm^3) for neutralisation. This 2nd titration is called a 'back-titration', and is used to determine the unreacted acid. 1.)Calculate the moles of HCl reacting with MgO. 2.)Calculate the mass of MgO that reacted with the initial HCl, hence the % purity of the MgO

Thank you for your help.

I think this is how it goes.. P Cl 22.5 100-22.5= 77.5% so. 22.5/31=0.726 77.5/35.5=2.18 0.726/0.726=1 2.18/0.726=3 PCL3 Second part P Cl 14.9 100-14.9=85.1 so 14.9/31=0.480 85.1/35.5=2.39 PCL5

I know how to calculate the empirical formula given the percentage masses; I’m just not sure what the hell is going on in the question. *Very confused* Thanks for your help anyway.

Hello all, I have some problems with a question and was wondering if there is a brilliant mind out there that could help. It would be much appreciated, thank you. The question states: A chloride of phosphorus, A, contains 22.5% P by mass. Reaction of this compound with more chlorine gives another chloride, B, containing 14.9% Calculate the empirical formulae of the two chlorides.

So do I.

So you're talking about when observing it, and not that the clock itself is speeding up. I miss understood you earlier...

Are you talking about the clock itself going faster if you move towards it, or that it seems to go faster if you look at it when moving closer?

The Doppler Effect in astronomy has to do with electromagnetic waves and not the distance between two objects.