Q: A chemist dips a penny into a hot zinc and sodium hydroxide solution, which causes the penny to turn a silvery color. What aspect of a
redox reaction did the zinc undergo when the penny was dipped into the solution?

A: Reduction

Why: I don't understand how this is a reduction, because a reduction is when you gain electrons and how does that correlate with the color? How would I do this if I were to solve this in 5 seconds (like I am supposed to)? Is there any trick or do I need to memorize this?
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Q: In general is there a trick to finding the # of isotopes an element has or is it just memorization?
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Q: Energy – Short Answer Scientists at Idaho National Lab have developed a new method to
refine biodiesel. The solvent in this method is composed of a high-pressure phase of what
molecule in which carbon is in its +4 oxidation state?

ANSWER: CARBON DIOXIDE (ACCEPT: CO2)

Why: I don't understand how to solve this. Is it memorization? I know how to calculate oxidation # and State, but this is sort of confusing.

Quote from: Avni on January 03, 2024, 12:07:13 AMQ: A chemist dips a penny into a hot zinc and sodium hydroxide solution, which causes the penny to turn a silvery color. What aspect of a
redox reaction did the zinc undergo when the penny was dipped into the solution?

A: Reduction

Why: I don't understand how this is a reduction, because a reduction is when you gain electrons and how does that correlate with the color? How would I do this if I were to solve this in 5 seconds (like I am supposed to)? Is there any trick or do I need to memorize this?
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Actually here Zinc is undergoing oxidation and not reduction.Zn is more reactive metal than Copper and silver.More reactive metal undergoes oxidation by losing electrons.
Practice it
The arrangement of metals as per reactivity series is: K > Na > Ca > Mg > Al > Zn > Fe > Ni > Sn > Pb > H > Cu > Ag > Au.
Remember more reactive metal can reduce less reactive metal.

Quote from: uma on January 06, 2024, 06:49:45 AM

Quote from: Avni on January 03, 2024, 12:07:13 AM___________________________________________________________________
Q: In general is there a trick to finding the # of isotopes an element has or is it just memorization?
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There is no need of memorizing the number of isotopes as every element has isotopes and number of isotopes can not be calculated or predicted by nay trick.
However it is important to know that H has three isotopes which we discussed in class also.
Make yourself familiar with some famous isotopes like C-14 used in estimating age of fossil fuel and U-238 for estimating the age of rocks.

Quote from: Avni on January 03, 2024, 12:07:13 AMQ: Energy – Short Answer Scientists at Idaho National Lab have developed a new method to
refine biodiesel. The solvent in this method is composed of a high-pressure phase of what
molecule in which carbon is in its +4 oxidation state?

ANSWER: CARBON DIOXIDE (ACCEPT: CO2)

Why: I don't understand how to solve this. Is it memorization? I know how to calculate oxidation # and State, but this is sort of confusing.

You know how to calculate oxidation number than you must add this in memory that +4 Oxidation number is the highest oxidation number of carbon and is in only CO₂ molecule.

Thank you!