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2

Calcium formate is a white-to-yellow or off-white crystalline powder, has a density of 2.02, solubility of ~17%, decomposes at $300^o$ C. It irritates eyes severely and has a stinging taste, therefore could have an "hard to describe odor" or effect on the nose. One mental conflict I have is that I would expect that measuring the density of a powder ...


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You need to be aware of the dilution formula in order to plot concentration on the x-axis and absorbance on the y-axis: $C_iV_i = C_fV_f$ So your initial concentration is your stock concentration and your initial volume is listed in the table. Your final volume is $\pu{100 mL}$. Can you determine $C_f$? With that you would be able to calculate all 5 ...


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Very good question. I believe you are talking about ordinary Bunsen burner flame which is considered a low temperature flame by atomic standards. Good temperatures for atomic emissions are on the order of the temperature of the surface of the Sun (around 10,000 K). So you are right, it is very "difficult" to visually distinguish the apparent flame ...


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Sodium flame is yellow, but all the light is due to two lines in the yellow region. If you look a sodium flame through a purple glass (cobalt glass), the yellow color is absorbed, and you do not see the sodium flame any more. The flame looks dark and colorless through a cobalt glass. On the contrary iron flame looks yellow, but it is made of a huge number of ...


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Following the advice of @Buck Thorn and @user1271772, I asked this same question over at the Cross Validated Stack Exchange. There, I received a very good answer and am providing the link for the interested reader: % coefficient of variation (%CV) for log-linear and log-log regression (calibrations) To summarise: yes, the formula is appropriate where the ...


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I think the major gas sensing technologies are NDIR(cheap), semiconducter type(cheapest), fuel cell type(cheap) and conductive polymers(expensive)


3

I want OP to understand that iodine ($\ce{I2}$) is not the one giving the starch solution deep blue color. It is rather triiodide ion ($\ce{I3-}$), which would form in presence of excess iodide ion ($\ce{I-}$): $$ \ce{I2 + I- <=> I3-} \tag1$$ This is an important aspect in iodometry titrations, because $\ce{I3-}$ is very water soluble compared to ...


3

Warning: This is also a homework question. However, this is more like mathematics (geometry) than chemistry, I decided to help you. Nonetheless, please keep in mind that we won't help you in all future perspectives, if you do not show your effort to solve the problem, regardless more mathematics involved. As M. Farooq pointed out that this problem can be ...


6

Starch is a long ribbon or a long filament made of a great number of glucose units attached to one another like the wagons in a train. But this filament is wound in a helicoidal way. And the inner part of this helix is a sort of long hole. And the dimension of this hole is just big enough to allow the iodine molecule $\ce{I2}$ to enter and stay there, ...


3

If we take 1st and last points on your graph we'd see that: At concentration $\pu{350ppm}$ your detector shows number $45$ At concentration around $0$ your detector shows number around $0$ So what if detector shows $175$ (which is $0.5*(350-0))$? You may conclude that the concentration is $\pu{22.5ppm}$ (which $0.5*(45-0)$) Calibration curve gives you ...


4

Suppose it is a calibration curve of high performance liquid chromatography (HPLC) to determine concentration of chloride ion in unknown solutions. The detector is sensitive to charge ions, which gave the peaks, area of which is proportional to concentration of ions. I assume each peak area is highly specific for ion in interest. First you make a calibration ...


6

I assume your teacher explained the HPLC separation. If injected a mixture of four ions you will get four peaks. Each peak has an area, which is proportional to the concentration of the substance. Imagine you wanted to determine the concentration of chloride ions in your tap water. What you would do is that you will prepare several known concentrations of ...


3

The line goes according to : $y = 0.1312~x$ ; In other words the area of the peak is equal to $0.1312$ times the concentration of chloride in ppm. This result is extremely useful. If for example, in a later measurement you obtain a peak whose area is $y = 35$, it means that the concentration $x$ of chloride ion responsible of this peak is : $x = 35/0.1312 = ...


1

Such problems in chemistry don't work out to infinite precision like pure math problems. You have to apply some chemical knowledge to the problem too. The book formula is obviously an approximation to the exact solution. To find the exact values expected you'd need to use combinatorics. Considering the chemistry: 7 carbons have a mass of 84, so a ...


1

This procedure from an MP-AES manufacturer features copper analysis (among other elements) without the use if hydrochloric acid. Hydrogen peroxide is used in this procedure but would not affect the extraction of copper. A copper standard is also available in "5% nitric acid" solution from the same company. So the people who are selling this ...


0

How to get a better turnover while maintaining a reasonably short reaction time? To speed up the reaction, you should look at changing (1) the reagents, (2) the catalysts, or (3) the reaction conditions. In particular you might be dealing with poor solubility for your alkyne substrate under 1. Reagents You could try the picolyl azides I mentioned in the ...


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Use ceric ammonium sulfate.[1,2] Quoting from reference 2: 2 Reagents (i) 0.25 per cent ceric ammonium sulphate in 8.8 N sulphuric acid. (ii) 40 per cent potassium thiocyanate solution. (iii) (a) Stock standard ferrous iron solution - 100 μg iron per ml. (b) Working standard ferrous iron solution - 0.3 to 10 μg iron per ml 2.2 Procedure To five ml of clear ...


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You are probably mixing natural abundance (NA) and relative abundance (RA). In mass spectrometry RA is a more valuable parameter as it can be directly obtained as the $y$-coordinate of a plotted mass spectra: the most abundant ion (isotope) corresponds to the base peak, which is always $100\%.$ In other words, RA reflect isotope ratio, not NA. For the ...


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Your advisor is making a pretty dangerous assumption (although sometimes pharma people do it). The assumption is that the impurity is structurally similar to the main compound and its UV-Vis spectrum is almost similar i.e., their extinction coefficients are the same. The idea in your formula is that the calibration curve for A will be same as B. Well that ...


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As you are looking for inventive ways to possibly measure Fe presence for a school presentation, may I suggest a crude (but likely interesting) visual aid in possibly determining relative iron concentration. One idea is that Fe ions in the presence of acidic H2O2 will engage in radical production. The latter reaction in the presence of suitable light over ...


3

There are iron testing kits in water which are available at an affordable price. I have not used them but read more about them here Testing iron in well water. You can test your spinach extracts for a yes no type answer if iron is present in significant quantities or not. Just keep in mind that PopEye's spinach is really not that rich in iron. Too much iron ...


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