chemistry help about primary standards?
Q. suggest reasons why anhydrous sodium carbonate is used as a primary standard but not sodium hydroxide.
Asked by HakS - Sun Jul 26 05:41:42 2009 - Chemistry - 2 Answers - Comments

A. Sodium hydroxide decomposes in the atmosphere. Primary standards need to be stable and not react with the surroundings. Sodium carbonate can be used against some aqueous acids.
Answered by Sam - Sun Jul 26 06:14:20 2009

three requirements for a chemical to be considered for use as a primary standard.?
Q. List and explain the importance of the three requirements. Thanks!
Asked by dchiu85 - Mon Jul 7 15:25:26 2008 - Chemistry - 2 Answers - Comments

A. it's 100% pure and anidrous it has to be not higly hygroscopic it has to be light insensitive it has to be termically stable
Answered by dvstudio 08 - Thu Jul 10 05:27:23 2008

Why is a deliquescent substance unsuitable for use as a primary standard?
Q.
Asked by SeRioUsLY - Mon Mar 24 00:45:33 2008 - Chemistry - 1 Answers - Comments

A. You must be able to weigh out the mass of a primary standard very accurately as it 'sets the standard' for other unknown concentrations to be calculated from. Deliquescent substances absorb water from the atmosphere and will eventually dissolve in that water. The exact amount of water they have absorbed at any time is impossible to know. So these substances are effectively changing their relative molecular mass (formula mass) all the time as they add more water. Obviously if you don't know the exact r.m.m. you can't produce a standard solution from them - you wouldn't know how much to weigh out!!! Hope this helps.
Answered by 24dnp - Mon Mar 24 08:16:07 2008

wat is primary standard and secondary standards in solutionz? y it called so?
Q. y there is no need of standardising primary standard solutions
Asked by Gayathri - Sat Oct 24 01:01:55 2009 - Engineering - 1 Answers - Comments

A. primary standards: 1)maintained at national labs in diff countries. 2)function is the calibration and verification of secondary standards. 3)used as ultimate reference standard secondary standard: 1)used as reference standard for calibration in labs in industries. 2)periodically sent to national labs for calibration with primary standards in the national labs primary standards are ultimate standard and are generally calibrated to wavelength standard which do not deteriorate with time and are easy to reproduce.
Answered by saurabh p - Sat Oct 24 10:39:03 2009

How much primary standard to weigh out?
Q. 1) what is the approx molarity of Na OH solution of 4g in 200m L water?? I got 0.455 M. is that correct? 2) Amount of KHP to be neutralized by 20 m L Na OH?? How do you determine how much KHP to weigh out for the titration?
Asked by hmmmm - Tue Feb 23 10:21:22 2010 - Chemistry - 1 Answers - Comments

A. 1) Sorry, but not correct: Molar mass Na OH = 40g/mol 4/40*1000/200 = 0.500M 2) 20ml of above solution will contain 0.4g Na OH = 0.4/40 = 0.01mol Na OH Na OH and KHP react in 1:1 mol ratio You will need about 0.01mol KHP Molar mass KHP = 204.2212 g/mol 0.01mol = 204.2212*0.01 = 2.04g KHP You do not laboriously weigh out exactly 2.04g of KHP. You very accurately weigh out an amount which is approximately 2.04g say +/- 0.2g. Titrate this against the Na OH solution, and calculate the molarity of the Na OH using the exact mass of KHP and the exact volume of Na OH used in the titration.
Answered by Trevor H - Tue Feb 23 10:54:50 2010

HI help PLZZ.Calculate the weight in grams of the primary standard solid oxalic acid needed to prepare 250 ml?
Q. Calculate the weight in grams of the primary standard solid oxalic acid needed to prepare 250 ml of a 0.200 N solution to be used in this laboratory exercise.
Asked by vana - Sun Feb 17 12:20:12 2008 - Chemistry - 1 Answers - Comments

A. There will be 0.2 moles of acid in 1 litre of solution. We want 250ml. of solution, therefore we need 0.2 * 0.25 = 0.05 moles of oxalic acid. Assume it is the doubly-hydrated form. Formula = HOOCCOOH.2H2O = C2H6O6 Molecular mass = 12 * 2 + 1 * 6 + 16 * 6 = 24 + 6 + 96 = 126 g/mole so 0.05 moles weighs 0.05 * 126 = 6.3g. We need 6.3g. of oxalic acid dihydrate to prepare 250ml. of a 0.2 mole/litre solution.
Answered by Blue Rizla Girl - Sun Feb 17 12:44:52 2008

Primary standards - Sodium Carbonate?
Q. What are some possible ways that could contribute to minor inaccuracies in determining the concentration of a prepared standard soidum carbonate solution? Any help is very much appreciated.
Asked by Marco L - Tue Jul 24 10:35:50 2007 - Chemistry - 1 Answers - Comments

A. You mean factors that leads errors in standardizing Na2CO3? If your Na2CO3 is analytical grade, then your Na2CO3 is a primary standard so you dont need to standardize it. Assuming you oven dry the Na2CO3, cooled, weighed and diluted with water, the molarity concentration is directly calculated as grams Na2CO3 times formula weight divided by the total volume of the solution in Liter. Some possible factors that contribute errors to your Na2CO3 concentration: -Undried Na2CO3 -Not cooled under dessicator -Not using Analytical grade substance -Not using calibrated analytical balance -In accurate volume dilution -Distilled water as diluent is not freshly prepared as it may possibly contains dissolved NOx, SOx etc. that could lead errors.
Answered by Alexis - Tue Jul 24 10:51:13 2007

what could be the salary package as per the international school standards for a primary teacher?
Q. teaching in India. English teacher
Asked by bubbles - Sun Nov 18 08:10:41 2007 - Teaching - 1 Answers - Comments

A. If it's a British curriculum international school (fairly common in India), the standard would be a British teacher's wage. This goes for just about all international schools, with the exception of where I.B. Programme is used. But even then, salary scales are usually pegged to a European country's. Best of luck.
Answered by SimonJ - Mon Nov 19 23:30:51 2007

What is the reason for heating a solid primary standard acid before using?
Q.
Asked by James - Thu Mar 27 18:50:36 2008 - Chemistry - 1 Answers - Comments

A. To dry it out. The most common primary standard acid is potassium hydrogen phthalate. It is purified to a high level by recrystallization. Then it is dried in an oven (not too hot!).
Answered by steve_geo1 - Thu Mar 27 18:57:12 2008

Why is oxalic acid a good primary standard for redox reaction AND acid base reactions?
Q. how come in redox titrations the oxalate ion needs to be heated?
Asked by NOYOU - Thu Jul 28 10:19:17 2011 - Chemistry - 1 Answers - Comments

A. Why is oxalic acid a good primary standard for redox reaction AND acid base reactions? a] it has a relatively high molar mass b] crystals can be obtained very pure and are neither hygroscopic or deliquescent formula: C2H2O4.2H2O c] very stable in solid form and not expensive d] as an acid can be used for acid- base reactions, and as readily oxised, also for redox reactions. how come in redox titrations the oxalate ion needs to be heated? It only need to be heated when being titrated with acod permanganate [manganate(VII)]. This is because it has quite a high activation energy, so needs to get to about 60C to get going. After this the reaction speeds up because of autocatalysis... one of the products Mn2+ ions catalyses the reaction, now… [cont.]
Answered by Colin - Thu Jul 28 11:52:48 2011

Which properties would be ideal in selecting the compound to be used as a primary standard for quantitative?
Q. Which properties would be ideal in selecting the compound to be used as a primary standard for quantitative volumetric analysis? A. Purity B. Vapor C. Hygroscopic D. Some Purity E. Expensive F. Not Hydroscopic G. Medium to High Molecular Weight H. Stable I. Liquid J. Volatile
Asked by junior_0889 - Sun Feb 22 00:13:03 2009 - Chemistry - 1 Answers - Comments

A. A, F, G, H, I
Answered by Zell - Sun Feb 22 17:37:29 2009

Sample primary standards based school report cards?
Q.
Asked by 1424easy - Tue May 9 16:44:28 2006 - Primary & Secondary Education - 1 Answers - Comments

A. ur an idiot, shut up.
Answered by tweek - Tue May 9 16:47:41 2006

Calculating an approximate Na OH concentration and preparing a primary standard of benzoic acid.?
Q. 1. An Na OH solution was prepared by dissolving approximately 4g of solid Na OH in 200 m L of water. Calculate and record the approximate Na OH concentration (MW = 40.00). 2. To prepare the primary standard, first calculate and record the expected mass of benzoic acid required to react in stoichiometric proportion with 20 m L of the Na OH solution (MW = 122.12). Record this amount.
Asked by Missy - Sun Apr 20 15:34:32 2008 - Chemistry - 1 Answers - Comments

A. Hi - this is not as hard as it looks - here's how you figure it out: 1. Na OH has a molecular weight of 40 (as you said), so 4 g is 1/10 of a mole (or 0.1 mol). Having this much Na OH in 200 m L (or .2 L) of water makes the concentration (.1) / (.2) = 1/2 mol/L (or 0.5 M) [M is for molar - the measure of molarity.] 2. Now, in stoichiometric proportion, 2 mol of Na OH are require for every 1 mol of benzoic acid (C6H5COOH), so we need (2 x .1 mol) = .2 mol. At a molecular weight of 122.12, that means we need 24.424g of benzoic acid. See the link below for more about benzoic acid and it's reactions (the only challenging part of this). Hope this helps!
Answered by opus23 - Mon Apr 21 18:43:53 2008

Why isn't hydrochloric acid used as a primary standard?
Q. And why is solid sodium carbonate stored in a desiccator prior to a volumetric analysis? Any answers to either are much appreciated, thank you.
Asked by Raven - Mon Apr 4 06:31:40 2011 - Chemistry - 1 Answers - Comments

A. A primary standard in metrology is a standard that is accurate enough that it is not calibrated by or subordinate to other standards. Primary standards are used to calibrate other standards referred to as working standards. Primary standards are used in analytical chemistry. Here, a primary standard is typically a reagent which can be weighed easily, and which is so pure that its mass is truly representative of the number of moles of substance contained. Features of a primary standard include: 1. High purity 2. Stability (low reactivity) 3. Low hygroscopicity and efflorescence 4. High solubility (if used in titration) 5. High equivalent weight 6. Non-toxicity 7. Ready and cheap availability 8. Eco-friendliness HCl, being a gas, does not… [cont.]
Answered by Trevor H - Mon Apr 4 06:42:16 2011

Calculate the wight in grams of the primary standard solid oxalic acid needed to prepare 250 ml of a 0.200 N s
Q. Calculate the weight in grams of the primary standard solid oxalic acid needed to prepare 250 ml of a 0.200 N solution to be used in this laboratory exercise.
Asked by vana - Sun Feb 17 11:13:23 2008 - Chemistry - 1 Answers - Comments

A. Are you using the anhydrous oxalic acid or the dihydrate? 1.Ahydrous. (COOH)2 Molar Mass - 90.03 But oxalic acid is a diprotic acid, so you would need 45.015g in 1litre solution to make a 1N solution. You want a 0.2N solution, so divde by 5, and you want 250m L, so divide again by 4.Answer 2.2508g 2 Dihydrate (COOH)2.2H2O Molar mass = 126.02g 126.02 2 5 4 = 3.1505g
Answered by Trevor H - Sun Feb 17 14:34:17 2008

What volume of 0.3126 M HCl is required to neutralize 0.2136g of Na2CO3, which is a primary standard in the?
Q. What volume of 0.3126 M HCl is required to neutralize 0.2136g of Na2CO3 (molecular weight is 106), which is a primary standard in the following chemical reaction? Na2CO3+2HCl=H2CO3+2Na Cl
Asked by funvonne - Tue Mar 11 15:23:12 2008 - Chemistry - 1 Answers - Comments

A. Moles Na2CO3 = 0.2136 g / 106 g/mol = 0.002015 Moles HCl needed = 2 x 0.002015 = 0.004030 V = 0.004030 / 0.3126 =0.01289 L =12.89 m L
Answered by Dr.A - Tue Mar 11 16:05:10 2008

Can oxalic acid be used as a primary standard to standardise a basic solution, such as sodium hydroxide?
Q. Thanks.
Asked by Purple Monkey Dishwasher - Sat May 16 03:23:45 2009 - Chemistry - 3 Answers - Comments

A. I checked through a list of recommended primary standards, which must meet a very high set of requirements to be so classified. Oxalic acid is not included in this list. This could be due to a number of reasons, such as for instance, hygroscopicity, indefinite end point among others.I do not know the exact reason. Here are the requirements of a good primary standard: A primary standard in chemistry is a reliable, readily quantified substance. Features of a primary standard include: 1. High purity 2. Stability (low reactivity) 3. Low hygroscopicity and efflorescence 4. High solubility (if used in titration) 5. High equivalent weight 6. It should be nontoxic 7. It should be readily available (inexpensive) 8. It should be environmentally… [cont.]
Answered by Trevor H - Sat May 16 03:59:42 2009

How do you know how much of the primary standard to be weighed when standardising it against a 2ndary standard
Q. For example how much of KHP to be weighed in standardising Na OH.
Asked by vibesguru - Thu May 22 21:45:35 2008 - Chemistry - 2 Answers - Comments

A. if you know the approximate strength of the Na OH, you determine the approximate # of moles that would be provided if you used about 3/4 of a full buret. it is a matter of accuracy, the more that comes out of the buret the less is the % error in the experiment. let's say it is appx a 0.1 Molar Na OH ( a common strength used because its drops have little strength & 1 drop past equivalence will usuallly produce an indicator color change) a 50 ml buret will give good accuracy with 37 ml + 0.037 litres @ 0.1mol/litre = 0.0037 moles of base you then weigh out 0.0037 moles of acid (since these react 1:1) 0.0037 moles KHP @ 204.22 g/mol = 0.75... grams --- you weigh out the grams , run the exp, then make adjustments in the amount of KHP so… [cont.]
Answered by Steve O - Fri May 23 00:15:41 2008

What's the difference between a Primary and Secondary Standard?
Q. I know a primary standard is a solution that can be accurately measured out (eg. KHP that has been dried and weighed). So a titration of KHP against Na OH will result in knowing the Molarity of the Na OH. Is the Na OH solution a secondary standard? thanks for your help:) thanks cm :)))
Asked by de-emt - Thu Jun 19 23:53:43 2008 - Chemistry - 1 Answers - Comments

A. No. Na OH is not a secondary standard. A secondary standard is the solution that you dilute from primary standard with a known dilution factor ( eg: a 2 times dilution of the primary standard) From your explanation, the Na OH in your experiment is the titrant.
Answered by CM - Fri Jun 20 00:08:39 2008

Suppose a sodium hydroxide solution were to be standardized against pure solid primary standard grade KHP. If ?
Q. 0.4538 g of KHP requres 44.12 m L of the sodium hydroxide to reach a phenophthalein endpoint, what is the molarity of the Na OH solution? Thanks soo much for the help (in advanced)!
Asked by Audrey W - Mon Oct 20 23:39:18 2008 - Chemistry - 1 Answers - Comments

A. well the equation for the molarity of Na OH solution for this information would be ... weight of KHP/ (molar weight of KHP)x(volume of Na OH) ***the molar mass for KHP is 204.22 grams/ mol ***also don't forget to change 44.12 ml to .04412 L ...so you would have (0.4538g KHP) / (204.22 grams/mol KHP) x (.04412 L Na OH) = .0504 M of Na OH
Answered by Heliosword - Mon Oct 20 23:54:34 2008