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Titrations or quantitative neutralization reactions between acids and bases are often recorded on graphs called titration curves or pH curves , which generally contain the volume of the titrant (or titrator that titrates an analyte or titrand) as the independent variable ( X -axis) and the pH of the solution as the dependent variable ( Y -Axis). An acid–base reaction can be used to determine pH via titration. pH  is a logarithmic scale used to specify the acidity or basicity of aqueous solutions. Acidic solutions (with higher concentrations of hydrogen ( H + ) cations) are measured to have lower  pH  values than basic or alkaline solutions. The neutral pH is 7 . A 𝑝𝐻 meter may be used for a precise and accurate measurement of the 𝑝𝐻 of a solution. The equivalence point, or stoichiometric point, of a chemical reaction is the point at which chemically equivalent quantities of reactants have been mixed. The endpoint refers to the point at which the indicator ch...

Tollens’ reagent , Fehling’s solution and Benedict’s reagent are known as mild oxidizers . Tollens’ reagent is the strongest among the three. Aldehydes test positive and ketones test negative to Tollens’ reagent, Fehling’s solution and Benedict’s reagent, in general. However, compounds having some other functional groups test positive as well. False positives are possible due to contaminations. All reagents are freshly prepared due to their short shelf lives. Tollens’ reagent: AgNO 3 (Silver nitrate) + NH 4 OH (Ammonium hydroxide) + NaOH (Sodium hydroxide) 2AgNO 3 (aq) + 2NaOH(aq) → Ag 2 O(s) + 2NaNO 3 (aq) + H 2 O(l) Silver oxide Ag 2 O(s) + 4NH 3 (aq) + 2NaNO 3 (aq) + H 2 O(l) → 2[Ag(NH 3 ) 2 ]NO 3 (aq) + 2NaOH(aq) Overall equation: 2AgNO 3 (aq) + 4NH 3 (aq) → 2[Ag(NH 3 ) 2 ]NO 3 (aq) Fehling’s solution: A . CuSO 4 (Copper(II) sulfate, blue) B . Potassium sodium tartrate ( (C 4 H 4 O 6 ) 2 2─ Na + K + ) + NaOH Benedict’s reagent: CuSO 4 + Sodium citrate ( (C 6 H 5 O 7 ) ─ Na + ...

The ideal gas law , aka the general gas equation, is the equation of state of a hypothetical ideal gas. It is a good approximation of the behavior of many gases under many conditions despite several limitations, and a combination of the empirical Boyle's law , Charles's law , Avogadro's law , and Gay-Lussac's law . The ideal gas law often takes an empirical form: pV = nRT where p, V, & T are the pressure, volume and temperature respectively; n is the number of moles; & R is the ideal gas constant. Mnemonic : p i V i n e RT = p ara i nfluenza V irus i n e RT Question: A 0.060 g piece of Magnesium was placed in Hydrochloric acid to generate Hydrogen according to the equation: Mg(s) + 2HCl(aq) → MgCl 2 (aq) + H 2 (g) The gas was collected at a pneumatic trough at 25 0 C . A barometer reading of 755 mm Hg  was made during the experiment. When the bubbles of Hydrogen ceased forming, the position of the bottle was adjusted so that the water level in th...

pH  is a logarithmic scale used to specify the acidity or basicity of aqueous solutions. Acidic solutions (with higher concentrations of hydrogen ( H + ) cations) are measured to have lower  pH  values than basic or alkaline solutions. The neutral pH is 7 . A 𝑝𝐻 meter may be used for a precise and accurate measurement of the 𝑝𝐻 of a solution. Mnemonic : ICE : I nitial C hange E quilibrium (molar concentration or partial pressure) Question: Report the expected pH in a range of two units difference when a 0.0100 M solution of Methylamine ( K b = 4.4 x 10 ─4 ) is prepared. Solution: Click/tap to enlarge the image α = Degree of dissociation, c = Molar concentration, B = Base NOTE: A weak base like Methylamine   ( CH 3 NH 2 )  is partl y ionized; and therefore, the molar concentration is NOT equal to the [OH ─ ] .  The concentration of undissociated water is nearly constant. Premonition about pH ❓ Let Chemaficionado know in the commen...

Reactivity  of an organic compound depends on several factors, and so does that of an  alkene  or an  alkyne ! An organic reaction takes place depending on multiple parameters including (but not limited to) the substrate(s), reagent(s), solvent(s), catalyst, reaction conditions,  viz ., temperature, pressure, moisture. For one, an isolated double bond (alkene) is more reactive than an isolated triple bond (alkyne) toward electrophilic addition ( A E ) reactions. This means saying an alkene is more reactive than an alkyne does not make sense as the reverse might be the case if the reaction conditions were different. Conjugated dienes are thermodynamically stable & kinetically unstable; however, methyl substitution on the allylic carbocation increases its stability by hyperconjugation. Question: Predict the major product(s) of the following reactions: Click/tap to enlarge the image Solution infographic: Click/tap to enlarge the image The curious case...

An acid–base reaction can be used to determine pH via titration. pH  is a logarithmic scale used to specify the acidity or basicity of aqueous solutions. Acidic solutions (with higher concentrations of hydrogen ( H + ) cations) are measured to have lower  pH  values than basic or alkaline solutions. The neutral pH is 7 . A 𝑝𝐻 meter may be used for a precise and accurate measurement of the 𝑝𝐻 of a solution. Titrations are quantitative neutralization reactions between acids and bases. The equivalence point, or stoichiometric point, of a chemical reaction is the point at which chemically equivalent quantities of reactants have been mixed. The endpoint refers to the point at which the indicator changes color in a colorimetric titration. The endpoint is related to the equivalence point, but these two are not necessarily the same. Four combinations of strong and weak (monoprotic) acid and (monohydroxy) base are possible. Polyprotic acid titrations have m...

Multistep synthesis  is the artificial execution of multiple organic chemical reactions to obtain one or more products by physical and chemical manipulations. Retrosynthetic analysis is a problem-solving approach in the organic syntheses, achieved by transforming a target molecule into simpler precursor structures regardless of any potential reactivity/interaction with reagents, and repeated until a simple or commercially available structure is reached, which can be used as a starting material to synthesize the target molecule. Polyvinyl acetate ( PVA or PVAc ), a rubbery synthetic thermoplastic polymer, which is commonly referred to as PVA glue, wood glue, white glue, carpenter's glue, school glue, or Elmer's Glue , is a widely available adhesive used for porous materials like wood, paper, and cloth. Question: Propose a synthesis of PVA by using any starting material with a maximum of two carbons and its derivatives BUT a reactant/reagent molecule that adds any carbon atom t...

It may sometimes look like there exists a correlation between the R/S  system and the D/L  system . However, the R/S system (absolute configuration) is NOT directly related to the D/L system (relative configuration). Let’s recall that the optical rotation is NOT directly related to the absolute configuration either. How to understand the relation between the optical rotation and the absolute configuration? Click HERE ! The side-chain of Serine has a hydroxyl group, −OH . If a thiol group, −SH , would substitute it to form Cysteine, the D/L labeling would not be affected by the swapping. However, this replacement would invert the molecule's R/S labeling, because the CIP (Cahn-Ingold-Prelog ) priority of CH 2 OH is lower than that of COOH but the CIP priority of CH 2 SH is higher than that of COOH .   Therefore, D- or L- does not necessarily mean R- or S- respectively! Since it is convenient to have the same label for the commonly occu...

Diethyl ether and other peroxide forming ethers like Tetrahydrofuran ( THF ) or Ethylene glycol dimethyl ether (1,2-Dimethoxyethane or DME , MeO(CH 2 ) 2 OMe) need to be avoided, and whenever used, are required to be handled with caution. Peroxide forming ethers are HazMats (hazardous materials). Unlike other alkyl ethers, Dimethyl ether (MeOMe) resists autoxidation. DME (not to be confused with 1,2-Dimethoxyethane, which is a peroxide forming ether, the acronym of which is also DME ) is relatively non-toxic, although it is highly flammable. The HFR (health, flammability, reactivity) rating of DME is 241 as per NFPA (national fire protection association) 704 fire diamond. A potentially major application of DME is as a substitute for Propane in LPG (liquefied petroleum gas) used as fuel in household and industry. DME may also be used as a blendstock in Propane autogas/gas. THF synthesis   Click/tap to enlarge the image Red ...

Dalton's law  ( aka  Dalton's law of  partial pressures ) states that the total pressure exerted is equal to the sum of the partial pressures of the individual gases in a mixture of non-reacting ideal gases. Partial pressures of the gases in a mixture tell us the relative number of particles or moles of the gases in that mixture. Question: Three 1 L flasks are connected to a 3 L flask by valves. The 3 L flask is evacuated to start with and the entire system is at 585 K . The first flask contains oxygen, the second hydrogen and the third nitrogen. The pressure of hydrogen is 1.65 atm . The amounts of gas molecules are proportional to their representations in the flasks. If valve 2 is opened first and then the rest of the valves is opened, what will the pressure be after the first valve is opened and after they all are opened? Assume the connections have negligible volume. Click/tap to enlarge the image Solution: Click/tap to enlarge the image Dandy Dalton's law❓ Let Ch...

A nucleophilic addition ( A N ) reaction is an addition reaction where an organic compound with an electrophilic double/triple bond reacts with a nucleophile s.t. the double/triple bond undergoes a cleavage. It’s often followed by an elimination of a (good) leaving group. Let’s remember that nucleophilicity and basicity are not the same thing! Fischer esterification or Fischer–Speier esterification is an esterification reaction by refluxing a carboxylic acid and an alcohol in the presence of an acid catalyst. Fischer esterification is typically an acid-catalyzed nucleophilic acyl substitution and stereoretentive. Most carboxylic acids are suitable for the reaction, but the alcohol should generally be primary/secondary as tertiary alcohols are prone to elimination. Due to steric and/or electronic effects in carboxylic acids, the reaction rate may differ significantly. Question: Predict which of the following will be easily esterified and why. If the introduction of the...