Why is it important to close the container of sodium borohydride after use?

If a solution contains 3 moles/liter of sodium chloride (nacl, made of sodium ions and chloride ions), what is the osmolarity of this solution

What is the volume of 3.2 moles of chlorine gas (cl2) at 295 k and 1.1 atm?

The image compares the arrangement of electrons in two different neutral atoms. a figure labeled atom q has a shaded sphere at the center of three concentric circles. the innermost circle has two black spheres. the middle circle has six black spheres. to the left of this figure is another figure labeled atom p. atom p has a shaded sphere at the center of three concentric circles. the innermost circle has two black spheres. the middle circle has seven black spheres. which of the following best explains the position of the two atoms in the periodic table?