WGU D425 INTRODUCTION TO CHEMISTRY
OA PRACTICE EXAMINATION 2026
QUESTIONS WITH ANSWERS GRADED A+
• Chemical Reaction.
Answer: Occurs when chemical bonds are formed or broken by atoms
colliding.
• Density of an object? mass of 2.4019 and volume of 1.40mL.
Answer: density = 1.7156g/mL= 1.72g/ml
• What is the equation used for concentration solutions?.
Answer: nA x MA x VA = nB x MB x VB 1. (n) number of H's in acid 2.
(M) Acid's Molarity 3. (V) Acid's Volume = Equals 1. (n) number of H's in
base 2. (M) Bases Molarity 3. (V) Bases Volume
• What is the freezing and boiling point of Celsius?.
Answer: Freezing: 0 Boiling: 100
• Physical Changes.
Answer: Do not alter the composition of matter.
• How many g in a kg?.
Answer: 1000g = 1 kg
• What is the freezing and boiling point of Kelvin?.
Answer: Freezing: 273.15 Boiling: 375.15 No Energy Present: 0
• Dilution Formula.
Answer: C1V1 = C2V2; initial concentration x initial volume = final
concentration x final volume
• Product.
Answer: Substance(s) produced at the end of a chemical reaction.
• what is the definition of an ion.
, Answer: at atom or a group of atoms that carries an electrical charge
• When does a chemical reaction occur?.
Answer: when chemical bonds are formed or broken by atoms colliding
• Intensive Property.
Answer: Depends on type of matter, not amount (e.g., density, temperature,
color).
• Trigonalbipyramidal.
Answer: 5 atoms bonded to central atom, 0 lone pairs
• Formula for Dilution.
Answer: C1V1 = C2V2 (initial concentration x initial volume = final
concentration x final volume).
• Ideal Gas Behavior.
Answer: Occurs under high temperature and low pressure.
• pH.
Answer: Measure of hydrogen ion concentration in a solution pH=-log[H+]
• given the balanced equation how many moles of hydrogen gas (H2) are
produced by the complete reaction of 2.11 x 10^22 atoms of Na 2Na (s) +
2HCl (aq) -> 2NaCl (aq) + H2 (g).
Answer: 2 Na+2 HCl → 2 NaCl+H2 2.11x1022atomsNa/6.022x1023=
0.0350 2 mol Na → 1 mol H2 0.0350/2=0.0175
• what is the percent composition for K in KCN?.
Answer: 60%
• converting moles to gas volume 4.96 moles of O2. At STP, 1mol = 22.4L
unknown: volumes of O2 calculate: 4.96 mol x 22.4 L/mol=.
Answer: 111.1 L
• a substance has a mass of 42.10g. if the density of the substance is known to
be 2.431g/ml what volume of substance is present.
Answer: 17.3ml
OA PRACTICE EXAMINATION 2026
QUESTIONS WITH ANSWERS GRADED A+
• Chemical Reaction.
Answer: Occurs when chemical bonds are formed or broken by atoms
colliding.
• Density of an object? mass of 2.4019 and volume of 1.40mL.
Answer: density = 1.7156g/mL= 1.72g/ml
• What is the equation used for concentration solutions?.
Answer: nA x MA x VA = nB x MB x VB 1. (n) number of H's in acid 2.
(M) Acid's Molarity 3. (V) Acid's Volume = Equals 1. (n) number of H's in
base 2. (M) Bases Molarity 3. (V) Bases Volume
• What is the freezing and boiling point of Celsius?.
Answer: Freezing: 0 Boiling: 100
• Physical Changes.
Answer: Do not alter the composition of matter.
• How many g in a kg?.
Answer: 1000g = 1 kg
• What is the freezing and boiling point of Kelvin?.
Answer: Freezing: 273.15 Boiling: 375.15 No Energy Present: 0
• Dilution Formula.
Answer: C1V1 = C2V2; initial concentration x initial volume = final
concentration x final volume
• Product.
Answer: Substance(s) produced at the end of a chemical reaction.
• what is the definition of an ion.
, Answer: at atom or a group of atoms that carries an electrical charge
• When does a chemical reaction occur?.
Answer: when chemical bonds are formed or broken by atoms colliding
• Intensive Property.
Answer: Depends on type of matter, not amount (e.g., density, temperature,
color).
• Trigonalbipyramidal.
Answer: 5 atoms bonded to central atom, 0 lone pairs
• Formula for Dilution.
Answer: C1V1 = C2V2 (initial concentration x initial volume = final
concentration x final volume).
• Ideal Gas Behavior.
Answer: Occurs under high temperature and low pressure.
• pH.
Answer: Measure of hydrogen ion concentration in a solution pH=-log[H+]
• given the balanced equation how many moles of hydrogen gas (H2) are
produced by the complete reaction of 2.11 x 10^22 atoms of Na 2Na (s) +
2HCl (aq) -> 2NaCl (aq) + H2 (g).
Answer: 2 Na+2 HCl → 2 NaCl+H2 2.11x1022atomsNa/6.022x1023=
0.0350 2 mol Na → 1 mol H2 0.0350/2=0.0175
• what is the percent composition for K in KCN?.
Answer: 60%
• converting moles to gas volume 4.96 moles of O2. At STP, 1mol = 22.4L
unknown: volumes of O2 calculate: 4.96 mol x 22.4 L/mol=.
Answer: 111.1 L
• a substance has a mass of 42.10g. if the density of the substance is known to
be 2.431g/ml what volume of substance is present.
Answer: 17.3ml
