What is the function of an erlenmeyer flask?

What is a metal replacement reaction

Give the set of reactants (including an alkyl halide and a nucleophile) that could be used to synthesize the following ether: draw the molecules on the canvas by choosing buttons from the tools (for bonds and charges), atoms, and templates toolbars, including charges where needed. ch3ch2och2ch2chch3 | ch3

Will mark brainliest how many electrons can be held in the energy level n = 4?