13
$6!\cdot 7!=10!$. Is there a natural bijection between $S_6\times S_7$ and $S_{10}$?
math.stackexchange.com

13
How much mass can be put in an L4 or L5 and it still maintain reasonable stability?
space.stackexchange.com

13
Are salts (e.g. NaCl) soluble in liquid metals?
chemistry.stackexchange.com

13
Why can't the reaction of grignard reagent with carboxylic acid give a ketone?
chemistry.stackexchange.com

13
What can I use as a fuel for an engine with carbon dioxide as the oxidizer?
chemistry.stackexchange.com

13
What purpose does mercury dichloride have in fireworks?
chemistry.stackexchange.com

13
The double-angle formula for cosine is expressible in terms of (single-angle) cosine alone; not so for sine. Why the asymmetry?
math.stackexchange.com

13
Which "exotic salt" can lower water's freezing point by 70 °C?
chemistry.stackexchange.com

13
Is chemistry finally seeing the end of the Haber-Bosch nitrogen fixation process?
chemistry.stackexchange.com

13
Prove that $23$ does not divide $2^n + 3^m$, for any $m, n \in \mathbb{N}$
math.stackexchange.com

13
I failed to make Claus benzene. (With sticks.)
chemistry.stackexchange.com

13
Is phosphorine (C₅H₅P) aromatic?
chemistry.stackexchange.com

13
Why is Earth's density gradient a step-function, rather than smooth?
earthscience.stackexchange.com

13
Why are there mountains/mounds in the centre of craters on the lunar surface?
space.stackexchange.com

12
Is there oxygen isotope exchange between dissolved CO2 and H2O?
chemistry.stackexchange.com

12
How do I derive metallic aluminum without electricity?
chemistry.stackexchange.com

12
Does water expand on freezing more than any other known substance?
chemistry.stackexchange.com

12
Are there any actual uses of isodiaphers?
chemistry.stackexchange.com

12
A curious coincidence: $\prod\limits_{k=1}^\infty\left(1+\int_{k}^{k+1}\left(\frac{\sin (\pi x)}{x}\right)^2\mathrm dx\right)\overset{?}{=}\pi/2$
math.stackexchange.com

12
How is the structure of triiodide ion (I3-) possible?
chemistry.stackexchange.com

12
Why are the densities of europium and ytterbium anomalously low?
chemistry.stackexchange.com

12
Is there any reason Cyanobacteria or Lichens can't survive on Mars?
space.stackexchange.com

12
Why is +3 a common oxidation state of gold?
chemistry.stackexchange.com

12
At high pressures, is aromaticity affected?
chemistry.stackexchange.com

12
When is $(x^p-1)/(p(x-1))$ a perfect square?
mathoverflow.net

12
How can a mug and a torus be equivalent if the mug is chiral?
math.stackexchange.com

12
Help with $\int _0^{\infty }\frac{\sinh \left(x\right)}{x\cosh ^2\left(x\right)}\:\mathrm{d}x$
math.stackexchange.com

12
What are the chances of finding an element in the outer solar system that otherwise can't be found on earth?
astronomy.stackexchange.com

11
How can a hefty sand storm happen in a thin atmosphere like Martian?
space.stackexchange.com

11
Where will we get nitrogen in space?
space.stackexchange.com

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