Neutral atoms get smaller as you move across the periodic table from (left to right) because the atom increases in electrons. The more electrons, the bigger the effective nuclear charge (electron and proton attraction) and so basically the atom shrinks.
It's a physical change because the composition of the salt hasn't change. Only the change in substance/form has occured. To tell if something has undergone physical change is:
• Melting
• Boiling
• Freezing
• Condensing
• Breaking
• Bending
• Dissolving
• Molecules can change motion and proximity
To tell if something changed chemically:
• Molecules rearrange with other molecules to make new substance
• Can be production of flames
• Color change
• Bubbling/fizzing
• Temp. change
• change in composition
Density of a solution is mass of solution per unit volume
Density = mass/volume
mass of solution is 46.08 g
volume of solution is 58.9 mL
since mass and volume is known, density can be calculated
density = 46.08 g / 58.9 mL = 0.78 g/mL
The mass of 165.0 g sample that remains after 90.0 minutes is 5.16 grams
calculation
lambda㏑2/18= 0.0385
m(t)= 165 x e( 0.0385 x90) =5.16g
