If you had 2 grams of NaCl vs 20 grams of NaCl, would the mass of each element in the compound change between these 2 amounts (2 vs 20 grams)? Would the percent by mass of any of the elements change? Explain.

No, the mass of each element in the compound would not change between these two amounts. In every 1 gram of NaCl there are 0.4 grams of Na and 0.6 grams of Cl. These are relative masses to Cl. If you had 2 grams of NaCl versus 20 grams of NaCl, you would have 0.8 grams of Na and 1.2 grams of Cl in the 2 gram sample and 8 grams of Na and 12 grams of Cl in the 20 gram sample. So the relative masses stay the same no matter how much NaCl is present. The percent by mass also would not change because it is based on relative masses to Cl which stay constant no matter how much compound there is present.

Step-by-step explanation

• The mass of each element in the compound would not change between these 2 amounts (2 vs 20 grams). The percent by mass of any of the elements would not change.No, the mass of each element does not change.  If a compound is a fixed ratio then that means that there is a specific amount of each element present no matter how much there is of the compound. 
• The percent by mass will not change either because it is based on the ratio of each element to each other and not on how much there is total. The only thing that changes when you have more or less is how many moles of each element are present.
• If you had 2 grams of NaCl vs 20 grams of NaCl, the mass of each element in the compound would not change between these 2 amounts. The percent by mass of these elements would not change either. This is because the amount of each element in the compound is constant regardless of how much NaCl is present.
• For example, if I have 2 grams of NaCl, then I have 1 gram of sodium ions and 1 gram of chloride ions. If I have 20 grams of NaCl, I still have 1 gram of sodium ions and 1 gram of chloride ions. This is because there are always 2 moles of chloride ions for every 1 mole of sodium ions in a salt crystal. Since we are comparing the same compound (NaCl) in both cases, we can assume that it has the same ratio of moles between its constituent elements (1:2).
• As a result, regardless if we have a large or small amount of NaCl, the percent by mass remains at 50% for each element since there is half as much salt as there is chlorine by mass (molar mass = 23 + 35 = 58 g/mol; 1 mole = 58 g/mol; therefore, half as much as chloride).
• If you had two gram of NaCl vs 20 grams of NaCl, the mass of each element in the compound would not change. This is because there are no differences in the number of atoms between 2 and 20 grams of NaCl. The percent by mass would not change either given that it is a constant value.
• The percent by mass can be found by dividing the molar mass of one element by the total molar mass of all elements present in a compound. For instance, when you calculate the percent by mass of chlorine in sodium chloride, you divide the molar mass of 35.5 g/mol (the molar mass of chlorine) by 58.44 g/mol (the total molar mass) to get 60.7%. Since this value does not change with quantity, it remains constant at 60.7% for any amount of sodium chloride.