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# Chemistry : Recent Questions and Answers

## Sign of change in enthalpy and change in entropy

Why is it wrong to assert that the change in entropy and the change in enthalpy must always have the same sign? What makes me think that they must have...

## What grade of sodium fluoride is needed for preservation of urine for drug and alcohol testing?

We are preparing DUI test kits and the distributor we purchased our sodium fluoride vials from is no longer in service. We are having difficulty finding a new supplier....

Asked on 12/04/2021 by Errin J

## Plasticisers and other impurities from polyethylene laboratory bottles?

Does polyethylene (PE), widely used for wash/squirt bottles in labs, contain soluble compounds such as plasticizers that can accumulate in organic...

## Calculating the amount of oxygen in a glass using candle burning time

I would like to calculate the amount of oxygen or concentration of oxygen in a glass or conical flask using candle burning time. I am thinking of a simple way...

Asked on 11/30/2021 by Fawaz Ahmed

## How to make Lithium medication from scratch

I take lithium carbonate as a medication. I was watching an "apocalypse-style" movie recently, which made me wonder how hard it would be to make my medication from scratch if...

## What is the most acidic proton of 2-methylcyclopent-2-en-1-one?

In an acid-base reaction of $ce{HO-}$ with 2-methylcyclopent-2-en-1-one, which is the most acidic proton? I had assumed it was one of them coming off C-5...

## Szabo and Ostlund's calculation of repulsion integral on page 172 via A.41

Returning to Szabo & Ostlund after a hiatus I tried to recreate his STO-3G calculation for HeH+ which begins on p. 168. It all went fine except for the two-electron,...

## Formal charge in a co-ordinate covalent bond

In coordinate bond, Does the donor atom have positive formal charge and the acceptor atom have negative formal charge? For example, in carbon monoxide the oxygen atom donates its lone...

Asked on 11/28/2021 by Wawa Abbass

## Is methylchloride reaction with water SN1 or SN2

I wanted to know if methylchloride reacting with $ce{H2O}$ would be SN1 or SN2. Methyl halide would not react using SN1 because methyl carbocation is very unstable but it...

## Why is 4-hydroxypyridine more acidic than benzoic acid?

4-hydroxypyridine (or 4-pyridone) has a $mathrm{p}K_mathrm{a}$ in the ballpark of $3$ to $3.33:^1$ (in the pdf linked below, the $mathrm{p}K_mathrm{a}$ of 1-methyl-4-pyridone has...