Practice Test 30 - High School Chemistry

20 questions. Answer them in any order, then submit to see your score and every explanation.

A student heats a blue solid in a dry test tube for 2 minutes using a hot plate. Observations/data: - Blue solid turns into a white powder - Droplets of liquid appear on the cooler upper part of the test tube - When the test tube is allowed to cool, the white powder stays white - Mass of test tube + contents: - Before heating: 48.62 g - After heating and cooling (open to air): 48.31 g Based on the evidence, did a chemical reaction occur? Choose the best CER justification.
Compare first ionization energy for magnesium and aluminum. Magnesium: [Ne]3s2 (group 2); aluminum: [Ne]3s2 3p1 (group 13). Aluminum's first ionization energy is lower than magnesium's. Which electron-configuration feature best explains why Al loses an electron more easily?
A concentration-versus-time graph for a reactant shows a section near the end where the curve is almost perfectly horizontal. What does the nearly horizontal section indicate about the reaction rate at that time?
Consider the balanced reaction: $2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}$ If you start with 3.0 mol $\text{H}_2$ and 1.0 mol $\text{O}_2$ , which reactant is the limiting reactant (runs out first)?
Carbon-14 undergoes beta decay as shown: $^{14}_{6}\text{C} \rightarrow {}^{14}_{7}\text{N} + {}^{0}_{-1}e.$ What type of radioactive decay is this?
Fluorine (F, atomic number 9) has 7 valence electrons and commonly forms F. How many electrons are transferred (gained or lost) when a neutral F atom becomes F, and why does this happen?
A teacher notes that aluminum (Al), in Group 13 and Period 3, tends to form $\text{Al}^{3+}$ ions in compounds. Which justification best explains why aluminum commonly forms a $+3$ ion?
A student claims: "When a gas forms in a reaction, mass is not conserved because bubbles appear." The student performs this test in a sealed syringe: $\text{H}_2\text{O}_2(aq) \rightarrow \text{H}_2\text{O}(l) + \text{O}_2(g)$ Mass of sealed syringe + hydrogen peroxide before: 80 g Mass of sealed syringe + contents after oxygen forms (still sealed): 80 g Which statement best addresses the student's claim?
A student observes that a reaction in a closed container speeds up when the container is gently warmed, even though the amounts of reactants stay the same. Which description best matches what happens to the reactant particles as temperature increases, according to collision theory?
A reaction is carried out in a sealed container: A(s) + B(s) → C(s). The masses are: - A = 14 g - B = 5 g After the reaction, the mass of product C is measured. What mass of C should be produced (assuming all reactants turn into C and nothing escapes)?
Lithium has electron configuration 1s2 2s1 and sodium has electron configuration [Ne]3s1. Sodium has a larger atomic radius than lithium. Which feature of the electron configurations best explains why?
A school is replacing old drinking-water plumbing. The district chose copper pipes instead of lead pipes. Water testing after replacement showed lead levels dropped from 18 ppb to <1 ppb, and copper levels remained below the action level. Which justification best supports the material substitution using chemical properties and evidence?
A lab group investigates: How does stirring speed affect the rate at which table salt dissolves in water? They add 5.0 g of NaCl to 100 mL of water at 25°C in identical beakers. Trial 1 is stirred at 0 rpm (no stirring), Trial 2 at 200 rpm, and Trial 3 at 400 rpm using the same magnetic stirrer and stir bar. They record how long it takes until the solution becomes clear with no visible crystals. Which is the independent variable?
A student mixes 25.0 mL of hydrochloric acid solution (HCl(aq)) with 25.0 mL of sodium hydroxide solution (NaOH(aq)) in a foam cup. Measurements are recorded before and after mixing. Before mixing: - HCl(aq): mass = 26.0 g, temperature = 22.0°C, appearance = clear/colorless - NaOH(aq): mass = 26.0 g, temperature = 22.0°C, appearance = clear/colorless After mixing (in the cup): - Mixture: mass = 52.0 g, temperature = 28.5°C, appearance = clear/colorless What does the data indicate about whether a chemical reaction occurred?
Write the electron configuration for the neutral fluorine atom (F, atomic number 9).
A shiny silver-colored spoon is left in a drawer for several months. When it is taken out, parts of the surface are dull and dark compared with the original shiny appearance. What observation best indicates a chemical change occurred?
A company is designing reusable water bottles for outdoor use. They tested two prototypes: (1) aluminum with an epoxy interior lining and (2) stainless steel with no lining. In a 30-day test with lemon-flavored water (acidic), the aluminum bottles showed a slight metallic taste in blind taste tests and the lining had small blisters near the threads; stainless steel bottles showed no taste change. The company selected stainless steel. Which option best justifies this decision using the evidence and chemical reasoning?
A student claims: "Adding a catalyst (manganese dioxide) increases the rate of hydrogen peroxide decomposition." The student collects oxygen gas from 20 mL of 3% H $_2$ O $_2$ using a gas syringe. Evidence: - Without catalyst: 10 mL of gas collected in 120 s - With MnO $_2$ : 10 mL of gas collected in 25 s - With MnO $_2$ : the solid MnO $_2$ appears unchanged after the reaction - The MnO $_2$ powder is black Which statement best evaluates how well the evidence supports the claim?
A nucleus emits a beta particle: $^{32}_{15}\mathrm{P} \rightarrow {}^{32}_{16}\mathrm{S} + {}^{0}_{-1}\mathrm{e}.$ Which quantity stays the same in this reaction?
A teacher shows three sealed videos of alkali metals reacting with water: lithium (Li, Group 1 Period 2), sodium (Na, Group 1 Period 3), and potassium (K, Group 1 Period 4). Which order (least vigorous to most vigorous) best matches the expected trend down Group 1?

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