# Tag Info

27

First, why other options are not really the options: A: vinegar, being a weak acid, doesn't neutralize sulfuric acid and only dilutes it; B: solid sodium hydroxide, a strong base, does neutralize sulfuric acid, but it does so vigorously releasing substantial amount of heat per unit of time: $$\ce{2 NaOH(s) + H2SO4(aq) -> Na2SO4(aq) + 2 H2O(l)}$$ Using ...

4

The Wikipedia article has a nice picture of the stages of deprotonation of phenolphthalein: https://en.wikipedia.org/wiki/Phenolphthalein However, there is a big jump here between H2In and In2-. In fact, smaller steps, showing just one deprotonation, are very reasonable. Whoever heard of two protons coming off at the very same time? http://www.ch.ic.ac.uk/...

3

I found this paper (it's in Japanese, but the relevant things are legible) https://www.jstage.jst.go.jp/article/yakushi1947/117/10-11/117_10-11_764/_pdf, which says that phenolphthalein has 2 pKas, pKa1 = 9.05 and pKa2 = 9.50. It also says that the pink form is the twice deporotonated; the 1- form exists, but is colourless.

3

Ignoring activities, activity coefficients, ionic strength effects, and so on, I get a pH of around 9.3. Given the 1 M concentration, I would not bet a lot of money on this, though. My solution, assuming a more typical solution concentration, is given in the two figures below. Sorry these are figures rather than proper formatting: I have been away for 3 ...

3

What you have gone wrong in this question is you completely disregard the fact that mentioned stronger acids than water are all in aqueous medium, in other words, dissolved in water. Thus, fast acid-base reaction ($\ce{H2O}$ acts as a base here) happens to give $\ce{H3O+}$ as the only acid in these mixtures (leveling effect of water). On the other hand, ...

3

This practice is done in analytical chemistry in order to minimize the relative weighing error on the balance. Preferring a larger formula weight for a primary standard has nothing to do with impurity levels. We have to start with the highest purity standard. For example, you wish to prepare a 0.010 M solution of oxalic acid dihydrate in 1 L flask. Its ...

2

This is an answer to a question of mine, which I posted a few days ago, Deprotonated form of phenolphthalein. I found this paper (it's in Japanese, but the relevant things are legible) https://www.jstage.jst.go.jp/article/yakushi1947/117/10-11/117_10-11_764/_pdf, which says that phenolphthalein has 2 pKas, pKa1 = 9.05 and pKa2 = 9.50. It also says that the ...

2

Yes, for example lysine. Lysine has two amino groups and one carboxyl group. When dissolved in aprotic solvents, all of these will be uncharged so the carboxyl group will be $\ce{-COOH}$ and the two amino groups $\ce{-NH2}$. When dissolved in water, these three groups have distinct $\mathrm pK_\mathrm a$ values of $2.15, 9.16$ and $10.67$. Depending on the ...

2

As you are probably aware, generalizations like "$\ce{BCl3}$ is a stronger Lewis acid than $\ce{AlCl3}$" can be problematic, as the results can be dependent on the base used and the conditions (eg solvent choice). That said, a common context for this ranking is with respect to carbonyl bases, such as in a Friedel-Crafts acylation. For these bases, $\ce{... 2 There are a few reasons. Some of the most important are: -Oxalic acid dihydrate isn't hygroscopic (it doesn't absorb water from the atmosphere, whereas sulfuric acid does). If a substance can absorb water from the atmosphere, then when you weigh it out, you won't be able to accurately calculate the number of moles used because you don't know how much is ... 1 In the case of o-nitrophenol, the acidic hydrogen is hydrogen-bonded to the nitro group's oxygen atom, making it less acidic. In the case of catechol, one acidic hydrogen is hydrogen-bonded to the adjacent OH group's oxygen atom, but the other, more acidic hydrogen is not hydrogen bonded. This hydrogen is more acidic than that of hydroquinone. The resulting ... 1 If you want to understand the reaction of$NaOH$on Aluminium, you may describe it this way. First, the aluminium reacts spontaneously with water, like sodium or calcium, producing gaseous Hydrogen$H_2$and an metallic oxide or hydroxide. With sodium or calcium, the hydroxide produced by this reaction quits the metal surface, and get dissolved, leaving a ... 1 See the stability of conjugate acid is very important. In case of secondary amine the basicity is appreciable but in guanidine system the conjugate acid is remarkably stable due to stabilizing conjugation that is occurring there. 1 A good way to compare basicity of basic compounds is to draw their corresponding conjugate acids and compare their stability. As you might figured out from drawing resonance forms of compound (2)'s conjugate acid (its protonated form ), the positive charge is going to be shared by the 3 nitrogens in the compound. On the other hand, in compound (4)'s ... 1 From Wikipedia, In chemistry, bases are substances that, in aqueous solution, release hydroxide (OH−) ions, are slippery to the touch, can taste bitter if an alkali, change the color of indicators (e.g., turn red litmus paper blue), react with acids to form salts, promote certain chemical reactions (base catalysis), accept protons from any proton donor ... 1 The mechanics of the reaction on Pb with concentrated HNO3 likely commences as follows:$\ce{Pb -> Pb(II) + 2 e-}\ce{HNO3 = H+ + NO3-}\ce{Pb(II) + 2 NO3- = Pb(NO3)2}\ce{H+ + e- = .H}\ce{.H + NO3- = OH- + .NO2}$(1997 Source) The literature also contains citations (see, for example, Page 37) of an associated mechanism involving ... 1$\ce{RSH}$is a better acid than$\ce{ROH}$(as the$\mathrm{p}K_\mathrm{a}$of$\ce{RSH}$is lower than the$\mathrm{p}K_\mathrm{a}$of$\ce{ROH}$, shown in a previous answer). This means that$\ce{RSH}$dissociates into$\ce{RS-}$and$\ce{H+}$more, i.e. the equilibrium below lies more to the right.$\ce{RSH + H2O <=> RS- + H3O+}\$ To compare ...

Only top voted, non community-wiki answers of a minimum length are eligible