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Introduction to Chemistry - Key Concepts and Calculations

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  • Express 450 × 10⁻⁹ m in decimal notation
    0.000000450 m (wavelength of blue light)
  • Express 0.000000001 s in scientific notation
    1 × 10⁻⁹ s (time it takes light to travel 1 ft)
  • How to determine the correct number of significant figures from a liquid measurement?
    Read the bottom of the meniscus on the graduated cylinder or balance display.
  • Identify significant zeros in 0.00010320 s
    Zeros after 1 and before 3 are not significant; zeros after 3 and before 2 are significant.
  • How many significant figures are in 1.30 × 10⁴ kg?
    Three significant figures
  • Perform calculation with correct significant figures: 89.3 × 77.0 × 0.08
    Result should have two significant figures, based on the least precise number.
  • Convert 195 km to hours at 24 mi/h
    Use unit conversion: 195 km × (0.621 mi / 1 km) ÷ 24 mi/h ≈ 5.06 hours
  • Is a penny with mass 2.49 g and volume 0.349 cm³ pure copper?
    Calculate density = mass/volume = 7.13 g/cm³; compare to copper density 8.94 g/cm³, so no.
  • Calculate mass of 17.56 mL acetone with density 0.7857 g/cm³
    Mass = density × volume = 0.7857 g/cm³ × 17.56 mL = 13.79 g
  • Convert 102 °F to Celsius
    C = (102 - 32) × 5/9 = 38.9 °C
  • Classify sugar dissolving in hot water
    Physical change
  • Classify carbon as element or compound
    Element
  • Classify urine as pure substance or mixture
    Mixture, heterogeneous
  • Number of neutrons in Fe-56 isotope
    30 neutrons (56 - 26 protons)
  • Which elements are alkali metals?
    Potassium and lithium
  • Predict ion formed by fluorine (F)
    F⁻ (gains one electron)
  • Calculate atomic mass of silicon from isotopes and abundances
    Weighted average of isotope masses based on natural abundances
  • Number of oxygen atoms in Fe₂(SO₄)₃
    12 oxygen atoms
  • Classify BaSO₄ as ionic or molecular compound
    Ionic compound
  • Write formula for calcium carbonate
    CaCO₃
  • Write formula for potassium permanganate
    KMnO₄
  • Write formula for chlorine monoxide
    ClO
  • Calculate formula mass of C₆H₁₂O₆
    180.18 g/mol
  • Find empirical formula for compound with 52.14% C, 13.13% H, 34.73% O
    C₄H₈O₃
  • Calculate moles in 0.46 g helium
    Moles = mass / molar mass = 0.46 g / 4.00 g/mol = 0.115 mol
  • Calculate mass of 1.32 mol carbon tetrafluoride
    Mass = moles × molar mass = 1.32 mol × 88.00 g/mol = 116.16 g
  • Calculate mass percent of Fe in FeCl₃
    Mass percent Fe = (mass Fe / molar mass FeCl₃) × 100%
  • Calculate empirical formula of naproxen from percent composition
    Use percent to mole conversion and ratio to find formula
  • Specific heat of copper
    0.385 J/g°C
  • Identify unknown substance with mass 0.4535 kg absorbing 4.37 × 10³ J with ΔT 21.7 °C
    Use q = m × c × ΔT to solve for specific heat and compare to known values
  • Calculate density of metal pyramid with mass 178 g and volume from dimensions
    Density = mass / volume; volume = (length × width × height) / 3
  • Density of gold
    19.3 g/cm³
  • Products of combustion of C₄H₉OH
    4 CO₂(g) + 5 H₂O(l)
  • Precipitation reactions are best classified as which type?
    Double displacement
  • What is a strong electrolyte solution?
    A solution that completely dissociates into ions in water, conducting electricity well