Miscellaneous Stuff From Unit 1

Question 0

Mass Number and Atomic Number Notation

Answer 0

Mass # -> 23

Na 11

Question 1

Dilution

Answer 1

M1V1 = M2V2

Ex: How would you prepare 250.0mL of a .500M HCl solution using a 12.0M stock solution of HCl?
Supplies: 250mL volumetric flask, graduated pipette, distiller water, HCl stock
.500M(250.0mL)=12.0M(V2) V2=10.4mL
Steps:
1. Fill flask halfway with water.
2. Slowly add 10.4mL into flask, swishing.
3. Use pipette to fill water up to the 250mL line.

Question 2

Percent Composition

Answer 2

Take the mass of each element in the compound and divide it by the molecular mass. Then multiply the decimal by 100.

Ex: MgO

Mol mass = 24 + 16 = 40 g/mol

Percent Mg = 24 / 40 X100 = 60%

Percent O = 16 / 40 X100 = 40%