How many moles of HCl are there in 15.0 mL of a solution with a concentration of 0.450 M?
A. 0.00675 mol
B. 3.00mol
C. 6.75 mol
D. 0.0300 mol

D)can be increased in a closed system

Ch4 and ph3 are both covalent since they are composed both of non-metals.    ch4 is non- polar because of  london forces and has a geometry of tetrahedral  ph3 , on the other hand, is umbrella shaped polar and has dipole-dipole intermolecular force (imf) . since ph3 is polar, it has a stronger imf   

Order of filling levels and sublevels of electrons: 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²3f¹⁴5d¹⁰6p⁶for an element with 5 electrons in the 3d energy level: full configuration: 1s²2s²2p⁶3s²3p³.