High school Lab. chemistry....?

Question

how can chemicals like common alum,boric acid,borax,sodium bicarbonate be identified with the help of simple CHEMICAL TESTS in the laboratory....cud u give the accompanying chemical reactions ?(pls use common lab reagents)

Answer 1

Alum is aluminum potassium sulfate, AlK(SO4)2. If you add NaOH, Al(OH)3 will precipitate at first. On continuing to add NaOH, however, the white precipitate will dissolve to give a clear solution of sodium aluminate, NaAl(OH)4.

Adding HCl to NaHCO3 will cause evolution of CO2 gas. NaHCO3 + HCl ===> CO2 + Na+ + Cl- + H2O.

Both boric acid, H3BO3, and borax, Na2B4O7, will give a green color in a flame test. Take a length of thin platinum wire, dip in dilute HCl and then into a gas burner flame to clean it. Then dip it into water solutions of boric acid or borax (clean again between tests). H3BO3 should give the straight green flame. Na2B4O7 will also show a bright yellow flame owing to sodium, Na+.

Answer 2

Try the following website. Either it has answer for the chemical in question or you could post a question to them. Try one item at time.
Just try try the words alum, boric acid etc one at time and you will see the existing questions & answers.


http://www.answerbag.com/c_view/2466

Answer 3

Lancenigo di Villorba (TV), Italy

If I understood your question, I should plan simplest cchemical tests for substances which you cited.

ALUMS
This is a family of mineral compounds whom containt Al, O and other chemical elements. You can dissolve this matter with warm concentrated sulphuric acid (WARNING! Concentrated sulphuric acid it is very corrosive reactive!!Don't add water to any amount of this acid!!).
That done, you chill to room temperature your liquid dissolution. That done, you take a little amount of solution and you add it to a larger ammonium hydroxide's solution.
Al(III) + 3 NH4OH <----> Al(OH)3 + 3 NH4+
WHAT COULD YOU SEE?
You will see white flake's precipitation (e.g. Al(OH)3).

BORIC ACID, BORAX
Nonetheless they appear very different (the former is available as aqueous solution, the latter is a family of vitrous matters) they containt trivalent boron atoms.
Boric acid's solutions went lied in a ceramic pot with ethanol (absolute ethylic alcohol), hence you add dropwise concentrated sulphuric acid (WARNING! Concentrated sulphuric acid it is very corrosive reactive!! Don't add water to any amount of this acid!!). This pot is warmed to direct flame's burner.
H2SO4 <---> H+ + HSO4-
H+ + CH3CH2OH <---> H2O + CH3CH2+
B(OH)3 + 3 CH3CH2+ <---> (CH3CH2O)3B + 3 H+
WHAT COULD YOU SEE?
You could see a pale grennish coloured flame (e.g. combustion of tri-ethoxy-boron's ether, (CH3CH2O)3B).

SODIUM CARBONATE AND BICARBONATE
These sodium's salts are known also in other denominations, respectively like Solvay's soda and sodium's hydrogeno-carbonate. Strong acidic solutions react with salts both, so developing gas bubbling (e.g. CO2).
Sodium bicarbonate is more reactive salt among two. Surely, acidic solution of HCl follows the underwrittens
NaHCO3 + HCl <---> NaCl + H2CO3
H2CO3 <---> H2O + CO2
WHAT COULD YOU SEE?
Foam (e.g. carbon dioxide, CO2) generates itself in the mix-vessel.

I hope this helps you.

Answer 4

ok, the style of moles of NaHCO3 is going to .043, because of the fact the mole ratio of NaHCO3 to CO2 is a million:a million. then you definately would desire to calculate the gram formula mass of NaHCO3. the gfm of Na is 23, H, a million C-12 O-sixteen so the entire gfm is 80 4. then you definately would desire to establish a share 1mol/(84g/mol) =.043/x. go multiply to get x=3.612 g/mol :)

Answer 5

colour change
volume change

Answer 6

hey i know about NaHCo3

Answer 7

the act of debasing a commercial commodity with the object of passing it off as or under the name of a pure or genuine commodity for illegitimate profit, or the substitution of an inferior article for a superior one, to the detriment of the purchaser. Although the term is mainly used in connexion with the falsification of articles of food, drink or drugs, and is so dealt with in this article, the practice of adulteration extends to almost all manufactured products and even to unmanufactured natural substances, and (as was once suggested by John Bright) is an almost inseparable - though none the less reprehensible - phase of keen trade competition. In its crudest forms as old as commerce itself, it. has progressed with the growth of knowledge and of science,, and is, in its most modern developments, almost a branch - and that not the least vigorous one - of applied science. From the mere concealment of a piece of metal or a stone in a loaf of bread or in a lump of butter, a bullet in a musk bag or in a piece of opium, it has developed into the use of aniline dyes, of antiseptic chemicals, of synthetic sweetening agents in foods, the manufacture of butter from cocoa-nuts, of lard from cotton-seed and of pepper from olive stones. Its growth and development has necessitated the employment of multitudes of scientific officers charged with its detection and the passing of numerous. laws for its repression and punishment. While for all common forms of fraud the common law is in most cases considered strong enough, special laws against the adulteration of food have been found necessary in all civilized countries. A vigorous branch of chemical literature deals with it; there exist scientific societies specially devoted to its study; laboratories are maintained by governments with staffs of highly trained chemists for its detection; and yet it not only develops and flourishes, but becomes more general, if less virulent and dangerous to health.

There are numerous references to adulteration in the classics. The detection of the base metal by Archimedes in Hiero's crown, by the light specific gravity of the latter, is a well-known instance. Vitruvius speaks of the adulteration of minium with lime, Dioscorides of that of opium with other plant juices and with gum, Pliny of that of flour with white clay. Both in Rome and in Athens wine was often adulterated with colours and flavouring agents, and inspectors were charged with looking of ter it.

In England, so far back as the reign of John (1203),(1203), a proclamation was made throughout the kingdom, enforcing the legal obligations of assize as regards bread; and in the following xeign the statute (51 Hen. III. Stat. 6) entitled " the pillory and tumbrel " was framed for the express purpose of protecting the 'public from the dishonest dealings of bakers, vintners, brewers, butchers and others. This statute is the first in which the adulteration of human food is specially noticed and prohibited; it seems to have been enforced with more or less rigour until the time of Anne, when it was repealed (1709). According to the Liber Albus it was strictly observed in the days of Edward I., for it states that: " If any default shall be found in the bread of a baker in the city, the first time, let him be drawn upon a hurdle from the Guildhall to his own house through the great street where there be most people assembled, and through the great streets which are most dirty, with the faulty loaf hanging from his neck; if a second time he shall be found committing the same offence, let him be drawn from the Guildhall through the great street of Cheepe in the manner aforesaid to the pillory, and let him be put upon the pillory, and remain there at least one hour in the day; and the third time that such default shall be found, he shall be drawn, and the oven shall be pulled down, and the baker made to foreswear the trade in the city for ever." The assize of 1634 provides that " if there be any manner of person or persons, which shall by any false wayes or meanes, sell any meale under the kinge's subjects, either by mixing it deceitfully or sell any musty or corrupted meal, which may be to the hurte and infection of man's body, or use any false weight, or any deceitful wayes or meanes, and so deceive the subject, for the first offence he shall be grievously punished, the second he shall loose his meale, for the third offence he shall suffer the judgment of the pillory and the fourth time he shall foreswere the town wherein he dwelleth." Vintners, spicers, grocers, butchers, regrators and others were subject to the like punishment for dishonesty in their commercial dealings - it being thought that the pillory, by appealing to the sense of shame, was far more deterrent of such crimes than fine or imprisonment. In the reign of Edward the Confessor a knavish brewer of the city of Chester was taken round the town in the cart in which the refuse of the privies had been collected. Ale-tasters had to look after the ale and test it by spilling some on to a wooden seat, sitting on the wet place in their leathern breeches, the stickiness of the " residue obtained by evaporation " affording the evidence of purity or otherwise. If sugar had been added the taster adhered to the bench; pure malt beer was not considered to yield an adhesive =extract. In 1553, the lord mayor of London ordered a jury of five or six vintners to rack and draw off the suspected wine of another vintner, and to ascertain what drugs or ingredients they found in the said wine or cask to sophisticate the same. At another time eight pipes of wine were ordered to be destroyed because, on racking off, bundles of weeds, pieces of sulphur match, and " a kind of gravel mixture sticking to the casks " had been found.

Similar records have come down from the continental European countries. -In 1390 an Augsburg wine-seller was sentenced to be led out of the city with his hands bound and a rope round his neck; in 1400 two others were branded and otherwise severely punished; in 1 435 " were the taverner Christian Corper and his wife put in a cask in which he sold false wine, and then exposed in the pillory. The punishment was adjudged because they had roasted pears and put them into new sour wine, in order to sweeten the wine. Some pears were hung round their necks like unto a Paternoster." In Biebrich on the Rhine, in 1482, a wine-falsifier was condemned to drink six quarts of his own wine; from this he died. In Frankfurt, casks in which false wine had been found were placed with a red flag on the knacker's cart, " the jailer marched before, the rabble after, and when they came to the river they broke the casks and tumbled the stuff into the stream." In France successive ordonnances from 1330 to 1672 forbade the mixing of two wines together under the penalty of a fine and the confiscation of the wine.