Unit 4 check
Unit 4 check: Chemical Reactions
10 questions from 9 lessons in Unit 4. Answer each one, and if you miss, follow the link back to where it is taught, then try again. Your score counts first tries.
Question 1 · from 4.1 · Sort it
Each card describes a physical change. Tap a card, then the kind of physical change it is.
A change of phase
Forming a mixture
Separating a mixture
Question 2 · from 4.2 · Calculate
Aluminum metal in a solution of copper(II) ions gives aluminum ions and copper metal: Al(s) + Cu²⁺(aq) → Al³⁺(aq) + Cu(s). Balance the equation with the smallest whole-number coefficients. What is the coefficient of Cu²⁺(aq)? Give a whole number.
Question 3 · from 4.3 · Sort it
Solutions of silver nitrate and potassium chloride, holding equal numbers of Ag⁺ and Cl⁻ ions, are mixed, and solid silver chloride forms: Ag⁺(aq) + Cl⁻(aq) → AgCl(s). Sort each set of ions by how a drawing should show it.
Packed together in a solid
Spread through the solution
Setup for question 4
Two students make claims about what happened in their experiments. Test each claim against the evidence.
Question 4 · from 4.4 · Decide and justify
A student dissolves 5.00 g of table sugar, sucrose (C₁₂H₂₂O₁₁), in water, and the crystals disappear. She evaporates all of the water and is left with 5.00 g of white crystals with the same properties as the sugar she started with. She claims that dissolving the sugar was a chemical process, because the crystals disappeared. Do her results support her claim?
Which reason supports your decision?
Setup for question 5
Baking soda, NaHCO₃, reacts with hydrochloric acid: NaHCO₃(s) + HCl(aq) → NaCl(aq) + H₂O(l) + CO₂(g). A student reacts a weighed sample of baking soda with more than enough HCl and collects the CO₂ at a fixed pressure.
Question 5 · from 4.5 · Fill the statement
Complete each prediction about the student's CO₂. Change only the one thing each sentence names.
If she uses twice the mass of baking soda, with the HCl still more than enough, the moles of CO₂ will change by a factor of . If she collects the gas at a higher temperature, at the same pressure, its volume will . If she uses HCl that is twice as concentrated, still more than enough, the moles of CO₂ will .
Setup for question 6
A student titrates 20.00 mL samples of an iron(II) solution with 0.02000 M potassium permanganate: MnO₄⁻(aq) + 5Fe²⁺(aq) + 8H⁺(aq) → Mn²⁺(aq) + 5Fe³⁺(aq) + 4H₂O(l). The permanganate ion is deep purple and the products are nearly colorless, so the first drop of permanganate that has no iron(II) left to react with leaves a faint purple color that lasts. The readings are a teaching example.
| Trial | Initial reading (mL) | Final reading (mL) | Color of the flask at the end |
|---|---|---|---|
| 1 | 0.20 | 19.45 | Dark purple |
| 2 | 0.35 | 18.73 | Faint purple |
| 3 | 0.10 | 18.52 | Faint purple |
Question 6 · from 4.6 · Multiple choice
Using the table: which trial's volume should the student leave out when she averages her results?
Setup for question 7
A student mixes reactants in four wells of a well plate and records what she sees. Her net ionic equation for each well is in the table.
| Well | Reactants | Observation | Net ionic equation |
|---|---|---|---|
| 1 | Na₂CO₃(aq) and CaCl₂(aq) | A white solid forms | Ca²⁺(aq) + CO₃²⁻(aq) → CaCO₃(s) |
| 2 | Zn(s) and HCl(aq) | The metal fizzes and dissolves | Zn(s) + 2H⁺(aq) → Zn²⁺(aq) + H₂(g) |
| 3 | NaOH(aq) and HNO₃(aq) | The well warms; nothing else changes | H⁺(aq) + OH⁻(aq) → H₂O(l) |
| 4 | KNO₃(aq) and NaCl(aq) | No change | No reaction |
Question 7 · from 4.7 · Decide and justify
Using the table: a classmate says well 2 is a redox reaction, even though hydrochloric acid is one of the reactants. Is the classmate right?
Which reason supports your decision?
Question 8 · from 4.8 · Spot the error
A student analyzes the reaction of formic acid with ammonia: HCOOH(aq) + NH₃(aq) ⇌ HCOO⁻(aq) + NH₄⁺(aq). Tap the line where the work first goes wrong.
Question 9 · from 4.9 · Match
Match each change to the electrons its balanced half-reaction shows.
Question 10 · from 4.1 · Match
Match each observation to the kind of evidence of a chemical change it shows.
0 of 10 answered.