Explain why sodium dihydrogen phsophate (NaH2PO4) is both an 'acid' and a 'salt'.
Firstly, why it is a salt
-Contains a positive metal ion(Na+) and a negative non metal ion (PO4*** ) whats the charge?
On why it is an acid:
It contains the H+ ions?
Well, my explanation should be improved, but where can I do so? Thank you!
2 more questions
A student tried to prepare 2 salts, barium sulphate and sodium nitrate using the method described in the paragraph below
Aqueous barium nitrate was mixed with aqueous sodium sulphate and the precipitate of barium sulphate was obtianed by filtration. The residue was dried in an oven
The filtrate was heated until the solution is saturated. Crystals of sodium nitrate was formed when the saturated solution was cooled
i. State one omission in the preparation of barium suplhate.
Surely not the part on drying in oven?(though it sounds weird) My guess is that he did not find out which was the salt in excess? Well.
2. Boron is a non-metallic element found in group III of the periodic table. It can be extracted from its oxide B2O3, by heating with powdered Mg in the absence of air. The products are boron and MgO.
ii After the reaction the boron is obtained from the reaction mixture by the following steps
i washing with warm dilute HCl acid (reason: to ensure Mg has been completely reacted and is not found on boron)
ii washing with a solution of NaOH ( to neutralise dilute HCl used to wash boron)
iii. washing with distilled water (to remove any remaining impurities found on boron)
Please help me check if the reasons I gave for the procedures are logical and correct
Also
What is the difference between Cl-37 and Cl - 35
My ans: They are isotopes of chlorine with different number of neutrons.
Originally posted by anpanman:Explain why sodium dihydrogen phsophate (NaH2PO4) is both an 'acid' and a 'salt'.
Firstly, why it is a salt
-Contains a positive metal ion(Na+) and a negative non metal ion (PO4*** ) whats the charge?
On why it is an acid:
It contains the H+ ions?
Well, my explanation should be improved, but where can I do so? Thank you!
Charge of PO4 is 3-
Regarding why its an acid, maybe talk about how it can behave like an acid which is to dissociate to give H+ ions and not use the word contain.
Originally posted by anpanman:2 more questions
A student tried to prepare 2 salts, barium sulphate and sodium nitrate using the method described in the paragraph below
Aqueous barium nitrate was mixed with aqueous sodium sulphate and the precipitate of barium sulphate was obtianed by filtration. The residue was dried in an oven
The filtrate was heated until the solution is saturated. Crystals of sodium nitrate was formed when the saturated solution was cooled
i. State one omission in the preparation of barium suplhate.
Surely not the part on drying in oven?(though it sounds weird) My guess is that he did not find out which was the salt in excess? Well.
ii After the reaction the boron is obtained from the reaction mixture by the following steps
i washing with warm dilute HCl acid (reason: to ensure Mg has been completely reacted and is not found on boron)
ii washing with a solution of NaOH ( to neutralise dilute HCl used to wash boron)
iii. washing with distilled water (to remove any remaining impurities found on boron)
Please help me check if the reasons I gave for the procedures are logical and correct
Also
What is the difference between Cl-37 and Cl - 35
My ans: They are isotopes of chlorine with different number of neutrons.
Both the reactants are aqueous so any ppt should be BaSO4 and thus whether there is any excess or not would not affect the BaSO4 obtained since yield is not part of the question i assume.
Where did the B from the ii) come from?
Originally posted by dkcx:Both the reactants are aqueous so any ppt should be BaSO4 and thus whether there is any excess or not would not affect the BaSO4 obtained since yield is not part of the question i assume.
Where did the B from the ii) come from?
Ok, missed out on the earlier part cuz it was found on another page. I have already edited the question. Thanks!
Originally posted by dkcx:Both the reactants are aqueous so any ppt should be BaSO4 and thus whether there is any excess or not would not affect the BaSO4 obtained since yield is not part of the question i assume.
Where did the B from the ii) come from?
Precisely. That's why the other option left is the "drying in oven" part. HAH..
Originally posted by anpanman:
Ok, missed out on the earlier part cuz it was found on another page. I have already edited the question. Thanks!
Have you considered what to do with the MgO that is together with your B? Think about it cos they didn't say how it was removed so your steps should involve that i believe.
Originally posted by anpanman:
Precisely. That's why the other option left is the "drying in oven" part. HAH..
Normally we don't dry things in the oven. We will always use a dessicator for drying of compounds since heat can cause the salt to loss its water of crystalisation and thus affect your product obtained.
Originally posted by dkcx:Have you considered what to do with the MgO that is together with your B? Think about it cos they didn't say how it was removed so your steps should involve that i believe.
Hi. Then what about the adding NaOH part?
HCl reacts with MgO to give MgCl and H2O. Now why do I add NaOH? Neutralise the remaining HCl? Or to react with MgCl? (I don't think it's possible)
Thanks
Originally posted by anpanman:
Hi. Then what about the adding NaOH part?HCl reacts with MgO to give MgCl and H2O. Now why do I add NaOH? Neutralise the remaining HCl? Or to react with MgCl? (I don't think it's possible)
Thanks
More to neutralise the HCl cos HCl will be added in excess to ensure its fully reacted while NaOH is normally added with pH being monitored usually with litmus paper.
for the part on why NaH2PO4 is acidic, use the dissociation of H2PO4 to explain, ie
H2PO4 + H2O --> HPO4 + H3O
H3O is the same as H+, hence, it is weakly acidic.
so.... wats the correct answer for the boron wan ? *confused
Originally posted by yiha093:so.... wats the correct answer for the boron wan ? *confused
HCl to react with MgO
NaOH to react with unreacted HCl
Water to remove any other impurities and also to wash away the NaOH
icic
but i think before adding water need stir to dissolve te sodium chloride.
but okay, i get the answer. tyty