15.3 Determine the mass of the following: 15.3.1. 2 mol calcium atoms 15.3.2. 0,3 mol nitrogen molecules
15.3.3. 0,5 mol table salt
15.3.4. 0,2 mol hydrochloric acid
15.3.5. 0,08 mol sodium carbonate (Na2CO3)
15.3.6. 0,25 mol ammonium sulphate (NH4)2SO4

Can someone me with questions 12 and 13 plz.

This chart lists four kinds of polymers and their sources. what can be known about all four polymers, despite their differences? they come from living things. they share ionic carbon bonds. they are at least 100 monomers long. they are made of repeating subunits.

Earth's axis of rotation is tilted at an angle of 23.5 degrees. what is one change you would see on earth if its axis was not tilted?