What is the concentration of a solution prepared by adding 50.0 ml of a 3.0 m hcl solution to a 250 ml volumetric flask and filling to the mark with water?

To solve this we use the equation, 

M1V1 = M2V2

where M1 is the concentration of the stock solution, V1 is the volume of the stock solution, M2 is the concentration of the new solution and V2 is its volume.

3.0 M (50 mL) = M2 (250 mL)

M2 = 0.6 M

The atoms of covalent materials are firmly bonded to each other in stable molecules, but these molecules are not generally very strongly attracted to other molecules of the material. This generally leads to low melting points in the covalent solids and high melting points in the ionic solids. For example, the carbon tetrachloride molecule CCl4, is a non-polar covalent molecule. Its melting point is -23 ° C. In contrast, the NaCl ionic solid has a melting point of 800 ° C.