How to convert from standard notation to scientific notation

    1. Find the first number between 1 and 10
    2. Place a decimal point and write remaining numbers
    3. Add x 10 to the right of the number in 2
    4. Count number of places needed to move decimal to create the original number
        • count right = (+) exponent
        • count left = (-) exponent
    5. Place the number you found in 4 as an exponent on the 10.
        • (+) exponent = counted right
        • (-) exponent = counted left

How to convert from scientific notation to standard notation

    1. Determine the exponent
        • (+) move decimal right
        • (-) move decimal left
    2. Move decimal in number before x 10 the number in 1 and place a decimal
    3. Add zero where no number exists

Significant Figures Rules

Leading zeros are not significant

  • 0.0032

Trailing zeros are signficiant

  • 0.003200
  • 10.00

Zeros inbetween real numbers are significant

  • 101
  • 0.00101

If the last place is a decimal, then all numbers are significant

  • 1250.

If a number is exact, then there are an unlimited number of significant figures.

  • Includes defined quantities

Tips on Writing Molecular, Total and Net Ionic Equations

Given: BaS (aq) + NH4Cl(aq)

Find Molecular, Total and Net Ionic Equations

    1. Determine products
      • BaS(aq) + NH4Cl(aq) → BaCl2 + (NH4)2S
    2. Balance molecular equation
      • BaS(aq) + 2NH4Cl(aq) → BaCl2 + (NH4)2S
    3. Determine Solubility of Products
      • BaS(aq) + 2NH4Cl(aq) → BaCl2 (aq) + (NH4)2S(aq)
    4. If soluble (aq) break into ions. Everything else stays together.
      • REMEMBER:
        • ions must have a charge
        • coefficients distribute just like in math
        • subscripts used for balancing become coefficients
      • Total Ionic Equation
        • Ba2+(aq) + S2-(aq) + 2NH4+(aq) + 2Cl-(aq) → Ba2+(aq) + 2Cl-(aq) + 2NH4+(aq) + S2-(aq)
    5. Lightly cross out what looks the same on both sides.
      • NOTE: If everything is crossed out - rewrite left side yields NR.
    6. Net Ionic Equation
      • Ba2+(aq) + S2-(aq) + 2NH4+(aq) + 2Cl-(aq) → NR