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Section 1: Chapters 1-4 - Chemical Foundations,
Atoms/Molecules/Ions, Stoichiometry, Types of Reactions & Solution
Stoichiometry
Q1: A sample of gold has a mass of 25.0 g and a volume of 1.29 cm³. What is the
density of gold?
A. 0.0516 g/cm³
B. 19.4 g/cm³
C. 32.3 g/cm³
D. 3.23 g/cm³
B. 19.4 g/cm³ [CORRECT]
Correct Answer: B
Rationale: Density = mass ÷ volume = 25.0 g ÷ 1.29 cm³ = 19.38 g/cm³ ≈ 19.4 g/cm³,
consistent with the known density of gold (19.3 g/cm³).
,Q2: Convert 2.54 cm to millimeters.
A. 0.254 mm
B. 25.4 mm
C. 254 mm
D. 0.0254 mm
B. 25.4 mm [CORRECT]
Correct Answer: B
Rationale: The prefix "milli-" means 10⁻³, so 1 cm = 10 mm. Therefore, 2.54 cm × 10
mm/cm = 25.4 mm.
Q3: A measurement is reported as 12.345 g. How many significant figures does this
value contain?
A. 3
B. 4
,C. 5
D. 6
C. 5 [CORRECT]
Correct Answer: C
Rationale: All non-zero digits are significant, and zeros between non-zero digits or after
a decimal point with a non-zero digit are significant. In 12.345, all five digits are
significant.
Q4: The result of multiplying 2.5 cm by 3.42 cm, reported with the correct number of
significant figures, is:
A. 8.55 cm²
B. 8.6 cm²
C. 8.550 cm²
D. 9 cm²
B. 8.6 cm² [CORRECT]
, Correct Answer: B
Rationale: In multiplication, the result should have the same number of significant
figures as the factor with the fewest significant figures. 2.5 has 2 sig figs; 3.42 has 3 sig
figs. The answer must have 2 sig figs: 2.5 × 3.42 = 8.55 → 8.6 cm².
Q5: According to Dalton's atomic theory, which statement is TRUE?
A. Atoms of different elements are identical in mass and properties
B. Atoms can be created and destroyed in chemical reactions
C. Each element is composed of extremely small particles called atoms
D. Compounds are formed by the physical mixing of atoms
C. Each element is composed of extremely small particles called atoms [CORRECT]
Correct Answer: C
Rationale: Dalton's atomic theory states that each element is composed of tiny,
indivisible atoms; atoms of different elements have different properties; atoms are
neither created nor destroyed in chemical reactions; and compounds form when atoms
combine in fixed whole-number ratios.