question 10. a chemist is studying the reactivity of various metals to design a safe experiment. she wants to identify elements that are less reactive than calcium (ca), a highly reactive metal. which of the following elements are less reactive than calcium (ca)? select all that apply
□ magnesium (mg)
□ sodium (na)
□ zinc (zn)
□ potassium (k)
□ iron (fe)

Question

Accepted Answer

# Brief Explanations: To determine which metals are less reactive than calcium (Ca), we refer to the metal reactivity series. The reactivity series (from most to least reactive for relevant metals here) is: Potassium (K) > Calcium (Ca) > Sodium (Na) > Magnesium (Mg) > Zinc (Zn) > Iron (Fe). So metals with lower reactivity than Ca are those below Ca in the series. Magnesium (Mg), Zinc (Zn), and Iron (Fe) are less reactive than Ca. Sodium (Na) is less reactive than K but more reactive than Ca? Wait, no, correction: The correct reactivity series order (for these metals) is K > Ca > Na? No, actually, the standard reactivity series (for alkali and alkaline earth metals and some transition metals) is: K > Ca > Na? Wait, no, let's recall correctly. The reactivity series (simplified for common metals): Potassium (K) > Sodium (Na) > Calcium (Ca)? No, no, that's wrong. Wait, the correct order (from most reactive to least, for these): K (most reactive), then Ca, then Na? No, actually, the reactivity of alkali metals (K, Na) and alkaline earth (Ca, Mg) and transition (Zn, Fe). The correct reactivity series (in order of decreasing reactivity) is: K > Ca > Na? No, no, let's check: Alkali metals: K is more reactive than Na. Alkaline earth: Ca is more reactive than Mg. Now, comparing Ca with Na: Ca is more reactive than Na? Wait, no, actually, the reactivity series (from high to low) is: K > Ca > Na? No, I think I mixed up. Let's use the standard metal reactivity series: Most reactive: K, Na, Ca, Mg, Al, Zn, Fe, ... (decreasing reactivity). Wait, no, correct order (from most reactive to least, for these metals): K (most), then Ca, then Na? No, that's incorrect. Wait, the correct reactivity series (based on electrochemical series or activity series) is: Potassium (K) > Sodium (Na) > Calcium (Ca) > Magnesium (Mg) > Aluminum (Al) > Zinc (Zn) > Iron (Fe) > ... Wait, no, actually, Calcium is more reactive than Sodium? Let's check the standard activity series. The correct activity series (from most reactive to least, for common metals) is: 1. Potassium (K) 2. Sodium (Na) 3. Calcium (Ca) 4. Magnesium (Mg) 5. Aluminum (Al) 6. Zinc (Zn) 7. Iron (Fe) 8. ... Wait, no, that's not right. Actually, Calcium is more reactive than Sodium? Let's verify with chemical reactions. For example, Ca reacts more vigorously with water than Na? No, Na reacts very vigorously with water, Ca also reacts but maybe less than Na? Wait, no, the standard activity series (from high to low) is: K > Ca > Na > Mg > Al > Zn > Fe > ... Wait, I think I was wrong before. Let's confirm: The reactivity of metals can be determined by their tendency to lose electrons. The electrochemical series (standard reduction potentials, but for reactivity, we look at oxidation, so reverse the potentials). The standard oxidation potentials (E°ox) for: K: E°ox = +2.93 V Ca: E°ox = +2.87 V Na: E°ox = +2.71 V Mg: E°ox = +2.37 V Zn: E°ox = +0.76 V Fe: E°ox = +0.44 V So higher E°ox means more reactive (since oxidation is loss of electrons, more positive E°ox means easier to oxidize, i.e., more reactive). So from the E°ox values: K (2.93) > Ca (2.87) > Na (2.71) > Mg (2.37) > Zn (0.76) > Fe (0.44). Ah, so that's the correct order. So K is more reactive than Ca, Ca is more reactive than Na, Na more than Mg, Mg more than Zn, Zn more than Fe. So the question is which metals are less reactive than Ca. So metals with E°ox less than Ca's (2.87 V). So Na (2.71) is less than Ca (2.87)? Wait, 2.71 < 2.87, so Na is less reactive than Ca? Wait, but K is more reactive than Ca (2.93 > 2.87). So let's re-express: Metals less reactive than Ca are those with E°ox < 2.87 V. So: - Na: 2.71 < 2.87 → less reactive than Ca? Wait, but earlier I thought Ca is more reactive than Na, but according to E°ox, Ca (2.87) has higher E°ox than Na (2.71), so Ca is more reactive than Na. Wait, that's correct. So Ca is more reactive than Na. Then Mg (2.37) < 2.87, Zn (0.76) < 2.87, Fe (0.44) < 2.87. K (2.93) > 2.87, so K is more reactive than Ca. So the metals less reactive than Ca are Na? Wait, no, wait: If Ca has E°ox 2.87, Na has 2.71, so Ca is more reactive than Na (since higher E°ox means more reactive). So Na is less reactive than Ca? Wait, but I always thought Na is more reactive than Ca, but according to the oxidation potential, Ca is more reactive. Let's check with water reaction: Na reacts vigorously with water, Ca also reacts vigorously, but which is more reactive? Let's see, the reaction of Ca with water: Ca + 2H₂O → Ca(OH)₂ + H₂. Na + H₂O → NaOH + H₂. The reaction of Ca with water is less vigorous than Na? Wait, maybe my E°ox is wrong. Wait, the standard reduction potential (E°red) for Ca²⁺ + 2e⁻ → Ca is -2.87 V, so E°ox (reverse) is +2.87 V. For Na⁺ + e⁻ → Na, E°red is -2.71 V, so E°ox is +2.71 V. So since E°ox (Ca) is higher than E°ox (Na), Ca is more reactive than Na. So Na is less reactive than Ca. Then Mg: E°red for Mg²⁺ + 2e⁻ → Mg is -2.37 V, so E°ox is +2.37 V < 2.87, so Mg is less reactive than Ca. Zn: E°red for Zn²⁺ + 2e⁻ → Zn is -0.76 V, E°ox +0.76 < 2.87. Fe: E°red for Fe²⁺ + 2e⁻ → Fe is -0.44 V, E°ox +0.44 < 2.87. K: E°red for K⁺ + e⁻ → K is -2.93 V, E°ox +2.93 > 2.87, so K is more reactive than Ca. So the metals less reactive than Ca are Magnesium (Mg), Sodium (Na), Zinc (Zn), and Iron (Fe). Wait, but let's confirm with the activity series. The standard activity series (from most reactive to least) is: K > Ca > Na > Mg > Al > Zn > Fe > ... Wait, if K is more reactive than Ca, Ca more than Na, Na more than Mg, etc. So yes, Mg, Na, Zn, Fe are less reactive than Ca, and K is more reactive. So the correct options are Magnesium (Mg), Sodium (Na), Zinc (Zn), Iron (Fe). Wait, but let's check again. Wait, maybe I made a mistake with Na. Let's see, the activity series (as per common textbooks) is: Most reactive: 1. Potassium (K) 2. Sodium (Na) 3. Calcium (Ca) 4. Magnesium (Mg) 5. Aluminum (Al) 6. Zinc (Zn) 7. Iron (Fe) ... Wait, this is conflicting with the E°ox values. So which is correct? Let's check a reference. According to the metal activity series (from high to low reactivity): K, Na, Ca, Mg, Al, Zn, Fe, Sn, Pb, (H), Cu, Hg, Ag, Pt, Au. Ah! So here, Na is more reactive than Ca? That's the confusion. So different sources might have slight variations, but the standard activity series (as taught in many chemistry courses) is K > Na > Ca > Mg > Al > Zn > Fe. Wait, that's different from the E°ox. So why the discrepancy? Because the activity series is sometimes simplified or based on different conditions (like reaction with water, acid, etc.). Let's check reaction with water: Na reacts very vigorously with water, Ca also reacts vigorously but maybe less than Na? So in terms of reaction with water, Na is more reactive than Ca. Then Ca is more reactive than Mg. So the activity series (simplified) is K > Na > Ca > Mg > Al > Zn > Fe. So in that case, Ca is less reactive than Na. So then, metals less reactive than Ca would be Mg, Al, Zn, Fe, etc., but Na is more reactive than Ca. So this is a critical point. So to resolve this, let's check the reactivity series from a reliable source. According to the Royal Society of Chemistry, the metal reactivity series (in order of decreasing reactivity) is: Potassium (K) > Sodium (Na) > Calcium (Ca) > Magnesium (Mg) > Aluminium (Al) > Zinc (Zn) > Iron (Fe) > Tin (Sn) > Lead (Pb) > Copper (Cu) > Silver (Ag) > Gold (Au) Ah, so here, Na is more reactive than Ca. So that means Ca is less reactive than Na. So then, the metals less reactive than Ca would be Mg, Al, Zn, Fe, etc. So in the given options: - Magnesium (Mg): less reactive than Ca (since Ca > Mg in the series) - Sodium (Na): more reactive than Ca (since Na > Ca), so not less reactive - Zinc (Zn): less reactive than Ca (Ca > Zn) - Potassium (K): more reactive than Ca (K > Na > Ca) - Iron (Fe): less reactive than Ca (Ca > Fe) So that's the correct analysis. So the mistake earlier was in the E°ox interpretation. The activity series (based on reaction with water, acid, etc.) is K > Na > Ca > Mg > Al > Zn > Fe. So: - Mg: less reactive than Ca (correct) - Na: more reactive than Ca (incorrect, so not less reactive) - Zn: less reactive than Ca (correct) - K: more reactive than Ca (incorrect) - Fe: less reactive than Ca (correct) So the correct options are Magnesium (Mg), Zinc (Zn), Iron (Fe). Wait, now I'm confused. Let's check a chemistry textbook. For example, the reactivity series (from most reactive to least) is: 1. Potassium (K) 2. Sodium (Na) 3. Calcium (Ca) 4. Magnesium (Mg) 5. Aluminium (Al) 6. Zinc (Zn) 7. Iron (Fe) 8. Tin (Sn) 9. Lead (Pb) 10. Hydrogen (H) 11. Copper (Cu) 12. Mercury (Hg) 13. Silver (Ag) 14. Gold (Au) So in this series, Na is more reactive than Ca, Ca more than Mg, etc. So that means Ca is less reactive than Na. Therefore, metals less reactive than Ca are Mg, Al, Zn, Fe, etc. So Na is more reactive than Ca, so Na is not less reactive. So where did the E°ox go wrong? Because the E°ox is a measure of the tendency to lose electrons in a redox reaction, but the activity series can be influenced by other factors like solubility of products, reaction conditions, etc. For example, when reacting with water, the product (hydroxide) solubility affects the reaction rate. NaOH is highly soluble, Ca(OH)₂ is slightly soluble, so the reaction of Ca with water might be less vigorous because the Ca(OH)₂ coats the metal, slowing down the reaction. So even though Ca has a higher E°ox (tendency to lose electrons), the reaction rate with water is lower than Na because of the product solubility. Hence, the activity series (based on reaction with water) places Na above Ca. So, to answer the question, we use the standard activity series (as taught in chemistry, K > Na > Ca > Mg > Al > Zn > Fe). Therefore: - Magnesium (Mg): less reactive than Ca (correct, since Ca > Mg) - Sodium (Na): more reactive than Ca (incorrect, since Na > Ca) - Zinc (Zn): less reactive than Ca (correct, Ca > Zn) - Potassium (K): more reactive than Ca (incorrect, K > Ca) - Iron (Fe): less reactive than Ca (correct, Ca > Fe) So the correct options are Magnesium (Mg), Zinc (Zn), Iron (Fe). # Answer: Magnesium (Mg), Zinc (Zn), Iron (Fe)

Sovi.AI - AI Math Tutor

QUESTION IMAGE

Question

Explanation:

Answer: