Training Chemistry Math Practice Test — Chemistry Math
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Practice Test — Chemistry Math

24 min Chemistry Math

Practice Test — Chemistry Math

A comprehensive review of stoichiometry, logarithms (pH), exponential decay, and equilibrium algebra.

Practice Test — 20 Questions

1. How many moles in 88 g of CO₂ (M = 44)?
2. Balance: $\text{Al} + \text{O}_2 \rightarrow \text{Al}_2\text{O}_3$
3. 48 g of carbon reacts with O₂ to form CO₂. How many grams of CO₂?
4. Find the pH if $[\text{H}^+] = 5 \times 10^{-6}$ M.
5. Find $[\text{H}^+]$ for pH = 11.
6. How many times more acidic is pH 2 than pH 6?
7. A 640 g sample has $t_{1/2} = 4$ days. How much after 12 days?
8. A fossil has 6.25% of its C-14. How many half-lives have passed?
9. Find $\lambda$ for $t_{1/2} = 20$ min.
10. Write the $K$ expression for $2\text{SO}_2 + \text{O}_2 \rightleftharpoons 2\text{SO}_3$.
11. If pH + pOH = 14 and pH = 4.5, find pOH.
12. What mass of NaCl (M=58.44) gives 0.5 mol?
13. $N(t) = 1000 \cdot (0.5)^{t/3}$. Find $N(9)$.
14. For $A \rightleftharpoons B$, $K=4$. Start with 2 M of A. Find $[B]$ at equilibrium.
15. Balance: $\text{C}_3\text{H}_8 + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O}$
16. What pH corresponds to $[\text{H}^+] = 1$ M?
17. After how many half-lives is 3.125% of a sample left?
18. If $K = 0.01$, are products or reactants favored?
19. A 10 g sample decays to 1.25 g. How many half-lives?
20. Is $\log_{10}(1000)$ equal to 3?
Show Answer Key

1. 2 mol

2. $4\text{Al} + 3\text{O}_2 \rightarrow 2\text{Al}_2\text{O}_3$

3. 4 mol C → 4 mol CO₂ → 176 g

4. $-\log(5 \times 10^{-6}) = 5.3$

5. $10^{-11}$ M

6. $10^4 = 10{,}000$ times

7. 3 half-lives → $640/8 = 80$ g

8. $0.0625 = (1/2)^4$ → 4 half-lives

9. $\ln 2/20 \approx 0.0347$ per min

10. $K = \frac{[\text{SO}_3]^2}{[\text{SO}_2]^2[\text{O}_2]}$

11. $14 - 4.5 = 9.5$

12. $0.5 \times 58.44 = 29.22$ g

13. $1000(0.5)^3 = 125$

14. $x/(2-x) = 4$ → $x = 8/5 = 1.6$ M

15. $\text{C}_3\text{H}_8 + 5\text{O}_2 \rightarrow 3\text{CO}_2 + 4\text{H}_2\text{O}$

16. pH = 0

17. $(1/2)^5 = 0.03125$ → 5 half-lives

18. Reactants

19. $1.25/10 = 1/8 = (1/2)^3$ → 3 half-lives

20. Yes

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