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A primary standard is usually a solid reactant that:

(1) is available in a high purity form

(2) does not change chemically when stored or exposed to air

(3) has a high formula weight to minimize errors in weighing

(4) is soluble in the solvent being used.

Sodium carbonate, Na 2 CO 3 size 12{ ital "Na" rSub { size 8{2} } ital "CO" rSub { size 8{3} } } {} , is commonly used as a primary standard base for standardizing acids, while potassium acid phthalate (KHP), KHC 8 H 4 O 4 size 12{ ital "KHC" rSub { size 8{8} } H rSub { size 8{4} } O rSub { size 8{4} } } {} , and oxalic acid dihydrate, H 2 C 2 O 4 2H 2 O size 12{H rSub { size 8{2} } C rSub { size 8{2} } O rSub { size 8{4} } cdot 2H rSub { size 8{2} } O} {} , are primary standard acids used for standardizing bases.

Na 2 CO 3 ( s ) + 2 HCl H 2 O + CO 2 + 2 NaCl size 12{ ital "Na" rSub { size 8{2} } ital "CO" rSub { size 8{3} } \( s \) +2 ital "HCl" rightarrow H rSub { size 8{2} } O+ ital "CO" rSub { size 8{2} } +2 ital "NaCl"} {} (4)

KHC 8 H 4 O 4 ( s ) + NaOH KNaC 8 H 4 O 4 + H 2 O size 12{ ital "KHC" rSub { size 8{8} } H rSub { size 8{4} } O rSub { size 8{4} } \( s \) + ital "NaOH" rightarrow ital "KNaC" rSub { size 8{8} } H rSub { size 8{4} } O rSub { size 8{4} } +H rSub { size 8{2} } O} {} (5)

( COOH ) 2 2H 2 O ( s ) + 2 NaOH Na 2 ( COO ) 2 + 4H 2 O size 12{ \( ital "COOH" \) rSub { size 8{2} } cdot 2H rSub { size 8{2} } O \( s \) +2 ital "NaOH" rightarrow ital "Na" rSub { size 8{2} } \( ital "COO" \) rSub { size 8{2} } +4H rSub { size 8{2} } O} {} (6)

The dry solid is carefully weighed on an analytical balance and then diluted in a volumetric flask to give a known molarity. The molarity of an acid or base is determined by titrating a measured volume of the acid or base with the primary standard. Then these acid or base solutions can in turn be used to determine the molarity of another acid or base (this is the case with the standardized solutions of NaOH and HCl used in this experiment).

In the example below a known amount of KHP will be titrated with a solution of NaOH to determine the NaOH solution concentration.

EXAMPLE: If 0.8168 g of KHP requires 39.35 mL of NaOH to reach the endpoint in a titration, what is the molarity of the NaOH? (1 mol KHP = 204.2 g)

0 . 8168 gKHP × 1 molKHP 204 . 2 gKHP 1 molNaOH 1 molKHP 1 39 . 35 mLNaOH 1000 mL 1L = 0 . 1016 mol / L = 0 . 1016 M size 12{0 "." "8168" ital "gKHP" times left ( { {1 ital "molKHP"} over {"204" "." 2 ital "gKHP"} } right ) left ( { {1 ital "molNaOH"} over {1 ital "molKHP"} } right ) left ( { {1} over {"39" "." "35" ital "mLNaOH"} } right ) left ( { {"1000" ital "mL"} over {1L} } right )=0 "." "1016" ital "mol"/L=0 "." "1016"M} {}

Notes on titration method:

1. Clean the buret until it drains smoothly.

2. Make sure the stopcock doesn't leak. The level should hold for ~3 minutes.

3. Remove air bubbles from buret tip before beginning. Rapid spurts usually work.

4. Rinse the buret two or three times with 5 mL portions of titrant (the solution you will use to titrate). Hold it horizontal and rotate to rinse.

5. Don't forget to record the initial reading. It does not need to be 0.00 mL.

6. Use a reading card to find the bottom of the meniscus.

7. Always read and record buret volumes to 0.01 mL.

8. Remember that the buret scale reads down, not up.

9. Put white paper under the flask to see color change easily.

10. Swirl the flask with one hand while turning the stopcock with the other or use stir bar and stir plate.

11. Add titrant slowly near the endpoint. Color that dissipates can be seen when getting close to endpoint.

12. Drops can be "split" by quickly turning the stopcock through the open position.

13. Near the endpoint use deionized water from wash bottle to rinse the flask walls from any splashed drops (adding water does not affect number of moles you have).

14. Don't drain buret below 25 mL (You won’t be able to determine final volume accurately). If necessary, read the buret level, refill, read the level, and continue. 

Calculation clarification

Amount neutralized by antacid 25ml of HCLThe amount of HCl that was neutralized by the fragment of the whole tablet, was only neutralized in part, this is where the titration comes in, the solution was still acidic, even after the dissolved antacid fragment, so the volume of NaOH used to finally cause the change in color is equal to the excess of HCl that was in the solution of HCl + water + antacid. So the number of moles of NaOH that was used is equal to the number of moles of HCl that was neutralized by the NaOH. So we DO use the formula in the procedure, so in the report form, where it had asked for the number of moles of HCl neutralized by the antacid:

n HC ln eutralizedbyAntacid = n HCladded n HClexcess size 12{n rSub { size 8{ ital "HC""ln" ital "eutralizedbyAntacid"} } =n rSub { size 8{ ital "HCladded"} } - n rSub { size 8{ ital "HClexcess"} } } {}

So then, this would be the 2 . 5 × 10 3 size 12{2 "." 5 times "10" rSup { size 8{ - 3} } } {} mol HCl–the excess which is calculated by converting the volume of NaOH used into moles, this number of moles then equals the number of moles oh HCl.

Volume NaOH titratedvolume excess HCl = volume titration of NaOH

Questions & Answers

what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
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how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Honors chemistry spring. OpenStax CNX. Mar 10, 2008 Download for free at http://cnx.org/content/col10512/1.9
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