Practice Test 8 - High School Chemistry

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

Fluorine (F) and iodine (I) are both halogens in Group 17. In a lab, fluorine reacts more vigorously with metals than iodine does. Which justification best explains this trend using periodic position and atomic structure?
A student argues: "If we just burn enough fuel, chemical reactions can match nuclear reactions in energy per atom." Which response best addresses the misconception?
A nucleus undergoes beta (beta-minus) decay: $^{131}_{53}\mathrm{I} \rightarrow \,^{131}_{54}\mathrm{Xe} + \,^{0}_{-1}\mathrm{e}.$ What changes in the nucleus during this decay?
Oxygen (O) has electron configuration [He]2s2 2p4 and fluorine (F) has electron configuration [He]2s2 2p5. Both are in period 2. Fluorine has a smaller atomic radius than oxygen. Which explanation best uses electron configuration to account for this trend?
In a simple displacement test, a strip of aluminum (Al) placed in a solution containing copper ions (Cu $^{2+}$ ) can produce copper metal over time, suggesting aluminum is more reactive than copper. Which justification best supports this observation using periodic-table reasoning and atomic structure (without needing a memorized reactivity series)?
Sulfur dioxide forms by $\text{S} + \text{O}_2 \rightarrow \text{SO}_2.$ If you have 7.0 mol S and 3.0 mol $\text{O}_2$ , what is the maximum amount of $\text{SO}_2$ that can form?
Calcium has electron configuration [Ar]4s2 and strontium has electron configuration [Kr]5s2. Strontium has a larger atomic radius than calcium. Which electron-configuration feature best explains why?
Given the balanced equation: $\text{N}_2 + 3\text{H}_2 \rightarrow 2\text{NH}_3$ How many moles of $\text{NH}_3$ form when $6.0$ mol of $\text{H}_2$ react completely?
An element X is in Period 3 and Group 2. Based on its periodic position, which prediction about its chemical behavior is most accurate?
A reaction is done in a sealed flask: $\mathrm{A(s) + B(aq) \rightarrow C(aq) + D(g)}$ . Masses placed into the sealed flask before the reaction: - A: 12 g - B solution: 18 g After the reaction, the gas $\mathrm{D}$ is still inside the sealed flask. What should be the total mass of all products inside the flask?
A student places 10 mL of hydrogen peroxide solution into a flask, then adds a small amount of yeast and gently swirls. Observations and measurements: - Within 10 seconds, many bubbles form and foam rises. - The flask becomes warm; temperature increases from 21.0°C to 32.0°C. - A glowing splint held near the mouth of the flask relights. - After 5 minutes, bubbling slows. - No solid product remains other than the yeast. Did a chemical reaction occur? Choose the best CER justification.
A student wonders why the Sun can shine for billions of years. The student compares (1) chemical burning like a giant fire and (2) nuclear fusion. Which statement best supports nuclear fusion as the Sun's long-term energy source?
A sodium atom (Na, atomic number 11) forms a sodium ion, Na. Which explanation best describes how neutral Na becomes Na and why the charge is +1?
Which set of coefficients balances the decomposition reaction (smallest whole numbers)? H2O2 → H2O + O2
Carbon monoxide forms by $\,2\text{C} + \text{O}_2 \rightarrow 2\text{CO}\,$ . If you start with $3.0\ \text{mol C}$ and $2.0\ \text{mol O}_2$ , which reactant is the limiting reactant?
Magnesium reacts with oxygen to form magnesium oxide: $\mathrm{2Mg + O_2 \rightarrow 2MgO}$ Which mole ratio correctly compares magnesium ( $\mathrm{Mg}$ ) to oxygen gas ( $\mathrm{O_2}$ )?
A reaction between dissolved ions begins immediately after two solutions are mixed, but the reaction is still noticeably faster when the mixture is stirred continuously. Which collision-theory explanation best accounts for stirring increasing the reaction rate?
Which process involves combining nuclei and typically requires extremely high temperature and pressure to overcome repulsion between positively charged nuclei?
Hydrogen peroxide decomposes according to $\mathrm{2H_2O_2 \rightarrow 2H_2O + O_2}$ . If $7.0\ \text{mol}$ of $\mathrm{H_2O_2}$ decompose completely, how many moles of $\mathrm{O_2}$ form?
Students study: How does temperature affect the reaction rate between sodium thiosulfate and hydrochloric acid? For each trial, they pour 50.0 mL of sodium thiosulfate solution into a flask and place it in a water bath set to 15C, 25C, or 35C. They then add 10.0 mL of 1.0 M HCl, swirl the flask the same way each time, and start a stopwatch. The flask sits on top of a paper with a black X; they stop timing when the X is no longer visible through the cloudy mixture. Which factors should be kept the same across trials to ensure a fair test?

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