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TEAS 7 Science: Chemistry practice questions

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These are original practice items written to the TEAS 7 blueprint (4 options, no penalty for wrong answers), not actual exam questions. Try each one before you open the answer.

What this topic covers

Science: Chemistry sits inside the Science section of the TEAS 7. Our bank holds 66 verified items tagged to it, and the 4 below are a fixed sample so the page stays the same every time you open it. Each one shows the reasoning, not just the letter.

The topic tag comes from our own items rather than from a published syllabus, so treat it as a map of what we cover. For the official section breakdown see the TEAS 7 page.

Science: Chemistry sample questions

Question 1

A solution has a pH of 3.0, and another solution has a pH of 5.0. How many times more hydrogen ions does the pH 3.0 solution contain compared to the pH 5.0 solution?

  1. A 1000
  2. B 100
  3. C 10
  4. D 2
Show the answer and explanation

Correct answer: B

The pH scale is logarithmic: each whole number change represents a tenfold change in [H+]. pH 3 has [H+] = 10^-3 M, pH 5 has [H+] = 10^-5 M. The ratio is (10^-3)/(10^-5) = 10^2 = 100. So the pH 3 solution has 100 times more hydrogen ions.

Why the other options are wrong:
A: A factor of 1000 corresponds to a 3-unit pH difference, not 2 units.
C: A factor of 10 corresponds to a 1-unit pH difference, not 2 units.
D: A factor of 2 would correspond to a pH difference of about 0.3, not 2 units.

Question 2

How many grams of oxygen gas (O₂) are required to completely react with 10.0 grams of hydrogen gas (H₂) to produce water? The balanced equation is 2H₂ + O₂ → 2H₂O. (Atomic masses: H = 1.008, O = 16.00)

  1. A 160.0 g
  2. B 79.4 g
  3. C 40.0 g
  4. D 20.0 g
Show the answer and explanation

Correct answer: B

Moles H₂ = 10.0 g / 2.016 g/mol = 4.96 mol. From the equation, 2 mol H₂ react with 1 mol O₂, so moles O₂ = 4.96 / 2 = 2.48 mol. Mass O₂ = 2.48 mol × 32.00 g/mol = 79.4 g.

Why the other options are wrong:
A: 160.0 g would be 5.00 mol O₂, far in excess of what is needed.
C: 40.0 g would correspond to 1.25 mol O₂, which is not the correct stoichiometric amount.
D: 20.0 g would be 0.625 mol O₂, insufficient to react with all the hydrogen.

Question 3

In a chemical reaction, 10.0 g of calcium carbonate (CaCO₃, molar mass 100.1 g/mol) reacts with 7.3 g of hydrochloric acid (HCl, molar mass 36.5 g/mol) according to the equation: CaCO₃ + 2 HCl → CaCl₂ + CO₂ + H₂O. What mass of carbon dioxide (CO₂, molar mass 44.0 g/mol) is produced if the reaction goes to completion?

  1. A 2.20 g
  2. B 3.65 g
  3. C 4.40 g
  4. D 1.82 g
Show the answer and explanation

Correct answer: C

Calculate moles: CaCO₃ = 10.0/100.1 ≈ 0.100 mol; HCl = 7.3/36.5 ≈ 0.200 mol. The stoichiometry requires 2 mol HCl per 1 mol CaCO₃, so both are present in exact ratio (0.100 mol CaCO₃ needs 0.200 mol HCl). Limiting reactant is either; both fully react. CO₂ produced = 0.100 mol × 44.0 g/mol = 4.40 g.

Why the other options are wrong:
A: 2.20 g is half the correct mass, possibly from using half the moles of CaCO₃ mistakenly.
B: 3.65 g would correspond to 0.083 mol CO₂, which might result from incorrectly using 2:1 ratio with HCl moles (0.200 mol HCl → 0.100 mol CO₂ → 4.40 g, not 3.65).
D: 1.82 g would come from a miscalculation like dividing instead of multiplying moles by molar mass.

Question 4

A solution has a pH of 3. Another solution has a pH of 5. How many times more acidic is the pH 3 solution compared to the pH 5 solution?

  1. A 100 times
  2. B 20 times
  3. C 2 times
  4. D 1,000 times
Show the answer and explanation

Correct answer: A

The pH scale is logarithmic; each whole number change represents a tenfold change in hydrogen ion concentration. A difference of 2 pH units (5 to 3) corresponds to 10^2 = 100 times more acidic.

Why the other options are wrong:
B: 20 times is not a correct multiple for a 2-unit pH difference.
C: 2 times would imply a linear relationship, but pH is logarithmic.
D: 1,000 times would correspond to a 3-unit pH difference.

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