The branch of chemistry concerned with identifying and quantifying the chemical constituents of matter.

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22 views

Copper(II) Oxide in the quantitative estimation of carbon and Hydrogen [on hold]

From the comments that the question has attracted, I have come to know that $\ce{CuO}$ acts as a catalyst in the combustion (in presence of excess of oxygen) of a hydrocarbon sample. Now my question ...
1
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0answers
9 views

SERS Gold nanoparticles performing poorly in organic solvents?

We have been working with some organic solvents lately and noticed a sharp decrease in SERS performance from our gold nanoparticles deposited in an organic solvent such as methanol. With reference to ...
3
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1answer
32 views

Chemical test for ferrous ions

I have a reference sheet for inorganic analysis which says that the confirmatory test for ferrous ions is as follows: "Make a solution of the given salt (whose cation is to identified) and add ...
1
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0answers
24 views

Qualititative inorganic analysis

Why is it that a specific order is followed while performing qualitative inorganic analysis? I mean, why are we told to first test for the anion in the given salt (and there is an order to be followed ...
1
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1answer
32 views

How to easily distinguish salts physically? Edit

I have basically 12 salts to identify in exams. They are *** Ammonium Carbonate, Ammonium Sulphate, Ammonium chloride, Aluminium Nitrate , Aluminium Sulphate, Barium chloride, Calcium Carbonate, ...
4
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24 views

An alternate purification process for sugar separation form bee honey?

Bee honey contains 75% sugars (Fructose, Glucose, Maltose, Sucrose and others), some water and low amount of different compounds (up to 5%) Wiki. Basic purification is done by addition of phosphoric ...
1
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1answer
15 views

What is the concentration of Ca2 in this solution if [OH–]? [closed]

Solid hydroxylapatite is dissolved in water to form a saturated solution. What is the concentration of Ca2 in this solution if [OH–] is somehow fixed at 2.70 × 10-6 M?
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2answers
40 views

What is the lowest mass measurable using a 4 decimal point analytical balance?

I think it is 1 mg, but I've heard people saying 0.1 mg. As 0.1 mg = 0.0001 g, which is the uncertain digit, I think such a measurement is not reliable at all. Any opinions ? Thanks.
11
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1answer
119 views

Acidity of HCl in Acetic Acid

A question asked to find the pKa of $\ce{HCl}$ in acetic acid. The equation of $\ce{HCl}$ disassociating in water is: $$\ce{HCl + CH3COOH \leftrightharpoons CH3COOH2+ + Cl-}$$ I predicted that the pKa ...
0
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0answers
7 views

Titrating cobalt II sulfate in a solution with Iron II sulfate

When titrating a solution of iron II sulfate and cobalt II sulfate using EDTA can ammonium flouride be used to mask the iron II in order to quantify the cobalt II without interference?
5
votes
1answer
111 views

How to extract water from a solution in formamide

I'd like to determine the water content in a sample without buying an expensive machine (like Karl Fischer titrator). So I'd like to measure the water volumetrically. I've chosen formamide to dissolve ...
0
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0answers
27 views

What causes differences in limits of detection?

I'm wondering what causes the limits of detection (LOD) to vary between different compounds, when calculated from the data obtained from one sample. I've analyzed a 0,1 µg/ml sample, containing ...
1
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0answers
32 views

The Lassaigne test and the metal used in it [closed]

Why should only sodium metal used for the Lassaigne test? Can used another metal for Lassaigne test? If yes which one should be used and why?
0
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0answers
7 views

Suitable technique for analysing the makup of polymer before photopolimerisation

I wonder which technique (or combination of techniques) would you use to analyse the state of a photopolymer. By state I mean, what is the ratio of monomers, oligomers, photoinitiator, impurities, ...
0
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0answers
32 views

unsure of how ppb concentration was calculated [duplicate]

YES this question is similar to a previous question of mine EXCEPT that the conversion factor they provide is different. If I were to use 10mL of the amount of mercury ion they are suggesting, I would ...
1
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0answers
25 views

Finding out the composition of seawater/brine?

as part of a project, I am working on precipitating salts from seawater and brine. I have a sample of seawater and I need to measure the concentrations of Mg2+, Ca2+ and Li+ present in the sample. As ...
0
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0answers
14 views

Why can't I use thiosulphate for backtitration?

My textbook says you only have to use thiosulphate for normal titration, eg. to measure the amount of iodine produced in a reaction. It states using it to reverse titration, eg. adding an excess ...
2
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0answers
24 views

Amount of Fe2O3 and Fe3O4 in a mixture of both containing impurities

An $\mathrm{8~g}$ sample of $\ce{Fe3O4}$ and $\ce{Fe2O3}$ containing some inert impurity was treated with excess of $\mathrm{aq}$ $\ce{KI}$ in acidic medium. which converted all iron to ...
1
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1answer
40 views

Internal Standard Methodology

I understand the use of the internal standard methodology, however I am unsure which values I should use in the equation as although I have been given the internal standard solution I also have ...
0
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1answer
41 views

Purity of calcium carbonate in limestone

$\mathrm{150~mL}$ of $\mathrm{0.1~N}$ $\ce{HCl}$ is required to react with $\mathrm{1~g}$ of a sample of limestone. Calculate percentage purity of calcium carbonate. Reaction: $$\ce{CaCO3 + 2HCl ...
3
votes
1answer
29 views

Absorption Spectrum Using a Spectrophotometer

After using a spectrophotometer, I have obtained absorbance values. To create an absorption spectrum, should I convert these values to percentage absorbance? (I've seen it in textbooks as such) If I ...
1
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0answers
21 views

What is the typical range for the molar absorptivity of paint?

For example, $\ce{TiO2}$ is used a lot as pigments in paint, what is the range of molar absorptivity for that? Would I be able to determine this from this graph: Ideally I could estimate a range ...
1
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0answers
31 views

spectroscopy as a pharmaceutical career [closed]

Is studying spectroscopy form it's fundamental perspective regarding "group theory" , "molecular schrodinger equation" and theoretical basis for IR & Raman analysis important for pharmacists ...
0
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0answers
21 views

Sulfur atomic absorption

Would the atomic absorption from FAA for Sulfur be from 3s2 -> 3p4 or 3p4 -> 4s0? I think according to the electronic partition function, there would be zero electrons in the 4s0 state at the ...
1
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0answers
33 views

How to Calculate Concentrations when Dissolving Two Salts

Some solid silver bromate was dissolved together with solid silver acetate what would be the highest achievable pH? Data $\mathrm{K_{sp ~\ce{(AgBrO3)}}} = 5.38 \times 10^{-5}~~~~~~~ ...
-1
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1answer
18 views

What chemical compounds used in qualitative chemistry can be distinguished by smell? [closed]

I will be competing in a contest and one part of it is qualitative analysis. And a fully legit way to help yourself during it is smelling compounds (to just get a theory to prove, you have to give a ...
1
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0answers
18 views

How to monitor (high) oxygen content in gas (air)?

How could I go about monitoring (semi-continuously, say, one measurement per 10 minutes) oxygen content in an oxygen-rich air mix (air with substantial amount of nitrogen removed with a Zeolite ...
6
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2answers
157 views

Short Cut Method to Calculating pH of Polyprotic Acid?

I am doing the following question: Calculate the pH of a $4.00\ \mathrm{mol\ L^{-1}}$ solution of citric acid. $\mathrm{pK_{a1}} = 3.09~~~~~ \mathrm{pK_{a2}} = 4.75~~~~~ \mathrm{pK_{a3}} = 6.40$ ...
0
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1answer
52 views

Can the concentration of a sodium carbonate solution be determined using volumetric analysis?

In the titration of sodium carbonate with hcl , isn't the first end point determined by phenol phthalene is equivalent to the volume of sodium carbonate because my text book say thats the volume at ...
3
votes
1answer
49 views

Reasons which explain why the efficiency of a reaction increases as the average rate decreases?

Reasons which explain why the efficiency of a reaction increases as the average rate decreases? in other words, why does a slow chemical reaction is more effective than quick ones? I done an ...
3
votes
1answer
49 views

Gravimetric analysis of barium or sulfate

Which is a better way to obtain barium sulfate precipitate for gravimetric analysis: by adding $\ce{Ba^2+}$ ions to sulfate ion solution, or the other way round? I think it is better to precipitate ...
9
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2answers
1k views

What is the accuracy of medical syringes?

I am interested in both low and high volume syringes.
0
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0answers
6 views

Sodium sulfate cells generate hydrogen and oxygen gas when a current is passed through the cell. [duplicate]

Sodium sulfate cells generate hydrogen and oxygen gas when a current is passed through the cell. For the following data, calculate the potienal required for the cell to generate partial pressures of ...
0
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0answers
12 views

Alcohol Concentration of Liquid Compared to Surrounding Gas

I am aware of the standard methods of calculating ABV by measuring specific gravity before and after fermentation using a hydrometer or refractometer, but would it be possible to accurately measure ...
1
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1answer
144 views

Significant figures when standard deviation is 0

For analytical chem lab, our group did a titration in which we got the same exact value every single time. As a result, our standard deviation was 0 and our instructor says to report answer using real ...
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0answers
39 views

How do I calculate the molecular mass of a complex in a complexometric titration with EDTA?

I had to titrate 0.35 mmol (3.2 g) of $\ce{Co2F2(Hdmpz)6(BF4)2}$ in a solution with 10 drops of 37 % $\ce{HCl}$, 10 mL of 4 M $\ce{NaOAc}$, 25 mL water and xylenol orange as indicator with a 0.05 M ...
5
votes
1answer
92 views

Error in Titration

When doing a titration with a burette, the error of the burette is usually $\pm 0.05\ \mathrm {ml}$, as we have to read two times on the burette (initial/final vol), the error will be $\pm 0.07\ ...
2
votes
1answer
64 views

NaOH solution not stable

$\ce{NaOH}$ solution can react with $\ce{CO2}$ to form sodium carbonate. Is there any other reason why $\ce{NaOH}$ solutions for accurate titrations cannot be stored for long (or the titre has to be ...
4
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1answer
91 views

Error propagation Titration

I hope I am right in this section. I am unsure with error propagation. When calculation the error in a titration, many errors has to be taken into account: Error in Glassware/ Error in Balance/ ...
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0answers
16 views

what causes the colour change in oscillating reaction? how can i time each oscillation time as accurately as possible? [duplicate]

BZ oscillating reaction this reaction consists of: Potassium Bromate Malonic Acid and Potassium Bromide Cerium Ammonium Nitrate in Sulfuric Acid 0.50% Ferroin Solution I wanted to know where these ...
2
votes
1answer
51 views

What type of test can I do to show that water is one of the products in a neutralisation reaction?

I've completed an acid base titration experiment of $\ce{HCl}$ and $\ce{NaOH}$. This forms salt + water $$\ce{HCl + NaOH -> NaCl + H2O}$$ Indicator was used and we evaporated the water to get the ...
1
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1answer
76 views

pH of a mixture of NaHSO4 and H2SO4 [closed]

Calculate the pH of a solution of $15\mathrm{~mM}$ $\ce{NaHSO4}$ and $1.50\mathrm{~mM}$ $\ce{H2SO4}$ at $25\mathrm{~^\circ C}$. The $\mathrm{p}K_\mathrm{a}$ of $\ce{HSO4-}$ at that temperature is ...
0
votes
1answer
34 views

Uncertainties after Averaging Trials [closed]

If I conducted 6 trials for a lab, all with the uncertainty of (+/- 0.1 mL)... After averaging the 6 trials to plot the results, what is the new uncertainty?
0
votes
0answers
36 views

How do I find the rate constant when I only have product concentrations? [duplicate]

I have done an experiment on the hydrolysis of aspirin, which is pseudo-first order. I need to find the rate constant, but I only have the final ($0.0278\mathrm{~M}$) and initial ($0\mathrm{~M}$) ...
1
vote
1answer
64 views

Validating a method to meet accuracy criteria using precision and accuracy?

If a method has a precision of 10% and an accuracy of 95 to 105% is required, can this method be validated to meet accuracy criteria? Explain your rationale. This question was posed by my professor ...
3
votes
1answer
51 views

Discerning Sodium bicarbonate

I have 'sodium bicarbonate' powder , which is supposed to be (NaHCO3) , is there a way for me to do a test on it at home , without some special equipment and determine whatever its 100% pure or it has ...
5
votes
1answer
76 views

Can chemicals be identified by their molar mass?

Wouldn't it be possible to identify a chemical by measuring its molar mass? How much accuracy does the measured molar mass need to be to guess what chemical it could be? EDIT: @ortho makes an ...
1
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0answers
44 views

Why aqueous ammonia is added to glucose solution to determine optical rotation?

In order to determine the specific rotation of glucose, it was mentioned in a practical chemistry book that 10g of dehydrated glucose must be dissolved in 80ml of water, then, adding 0,2ml of aqueous ...
4
votes
1answer
120 views

Hybridization, MOT and Paramagnetism

In what way can hybridization or molecular orbital theory be used to explain paramagnetism? For instance, when something is hybridized to make enough bonding electrons, do all the electrons end up ...
5
votes
1answer
66 views

Difference in calculated pH and the real pH of a phosphate buffer?

I'm from Colombia and I joined this site to ask a question that I could not solve yet. I am calculating the amounts to prepare a phosphate buffer with two salts. I want to prepare a buffer system with ...