This one as well in the picture below. Need done asap please.

Different isotopes indicate that an element will have different numbers of

Astudent carefully transfers 30 g of water and 30 g of alcohol in a glass tube, forming two layers and filling the tube completely. after sealing the tube, the student mixes the solutions, and notices a bubble that forms in the tube. what is the mass of the contents in the glass tube after mixing?

Which element has the lowest electronegativity? calcium(ca) gallium(ga) selenium(se) bromine(br)