Practice Test 33 - High School Chemistry

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

Engineers propose using a radioisotope power source (a device that uses heat from radioactive decay) to power a robotic spacecraft in deep space where solar panels are less effective. The benefit is long-lasting, compact power for exploration and scientific instruments. The concern is ensuring the radioactive material stays contained during launch and in any accident, to prevent environmental contamination. Which statement best balances the benefits and risks?
Oxygen is in group 16 with 6 valence electrons ( $[He]2s^2\,2p^4$ ). Oxygen often forms two bonds in molecules such as H $_2$ O. Which explanation best connects oxygen's valence electrons to forming two bonds?
Calcium reacts with hydrochloric acid: $\text{Ca} + 2\text{HCl} \rightarrow \text{CaCl}_2 + \text{H}_2$ If you have 3.0 mol Ca and 4.0 mol HCl, what is the maximum amount of $\text{H}_2$ that can form?
For the balanced reaction: $\textbf{N}_2 + \textbf{3H}_2 \rightarrow \textbf{2NH}_3$ If $6.0\ \text{mol}$ of $\text{H}_2$ react completely, how many moles of $\text{NH}_3$ form?
Two product curves are shown on the same concentration-versus-time graph. Both eventually reach a similar plateau, but Curve A rises more steeply than Curve B during the early part of the reaction. What can you conclude?
In a sealed plastic bag, a student combines 12 g of solution A and 8 g of solution B. A solid precipitate forms (A(aq) + B(aq) → AB(s)). The mass of the sealed bag and its contents is measured: - Before mixing: 120 g - After reaction: 120 g Which conclusion best matches these data?
Chlorine has atomic number 17. How many valence electrons does a neutral chlorine atom (Cl) have?
A carbon-14 nucleus changes into nitrogen-14 by emitting a beta particle (an electron). Which type of nuclear process is this?
A student leaves a cut apple slice on the lab bench. After 20 minutes it turns brown. The cafeteria manager wants to know if the browning is a chemical change (forming new substances) so they can choose a treatment to slow it down. Design an investigation to test whether the browning is due to a chemical reaction with oxygen. Which plan is best?
Aluminum reacts with chlorine gas to form aluminum chloride: $2\text{Al} + 3\text{Cl}_2 \rightarrow 2\text{AlCl}_3$ If $4.0\ \text{mol}$ of $\text{Al}$ react completely, how many moles of $\text{Cl}_2$ are needed?
Two alkaline earth metals—magnesium (Mg, Group 2 Period 3) and calcium (Ca, Group 2 Period 4)—are each placed into separate containers of water at the same temperature. Which metal reacts faster with water?
Fluorine (F) has electron configuration [He]2s2 2p5 and chlorine (Cl) has electron configuration [Ne]3s2 3p5. Fluorine has a smaller atomic radius than chlorine. Which statement best explains why using electron shell ideas?
Magnesium (Mg) has electron configuration [Ne]3s2 and chlorine (Cl) has electron configuration [Ne]3s2 3p5. Both are in period 3 (same number of occupied shells). Chlorine has a smaller atomic radius than magnesium. Which statement best explains this trend using electron configuration ideas?
Balance the chemical equation using the smallest whole-number coefficients: Na + Cl2 → NaCl
Carbon (C) has 4 valence electrons (electron configuration ends in $2s^2\,2p^2$ ). Carbon commonly forms 4 bonds in molecules such as $\text{CH}_4$ . Which explanation best connects carbon's atomic structure to this bonding behavior?
A magnesium ion is $\mathrm{Mg^{2+}}$ and the isotope is magnesium-24 ( $^{24}$ Mg). How many electrons are in $\mathrm{^{24}Mg^{2+}}$ ?
A student adds a spoonful of baking soda to a cup of vinegar at room temperature. During mixing, the liquid starts fizzing rapidly and the cup feels cooler to the touch. Which observation is evidence that a chemical reaction occurred (new substances formed)?
In the reaction $2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}$ , which bond change is associated with energy being released to the surroundings?
A student adds yeast to warm sugar water in a sealed bottle with a thermometer attached. Over time, the thermometer reading rises from 25°C to 28°C while gas bubbles form. Based on the temperature increase, what best describes the energy transfer during this biological reaction (respiration/fermentation)?
Two beakers contain the same volume of solution and the same type of reactant particles. Beaker A is dilute, and Beaker B is concentrated. Both are kept at the same temperature and stirred the same way. Using collision theory, what is the best explanation for why Beaker B reacts faster?

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