Does molar mass vary if the substance is the same? Does having different molar masses mean the substances are different?

Can someone me with 6 to 10 plz this is for masteries test.

Which of the following notations would be the appropriate and final way to display the formula for magnesium chloride a. mgcl2 b. mg+2cl–1 c. mgcl2 d. mgcl

The concentration of ionic substances is important for the heart to beat. your heart responds to electrical impulses that travel through heart cells that are made up mostly of water. which properties of ionic compounds are important to support this function? solubility in water conductivity crystalline melting point