Problem: Given the question: Given the background: Many reactions take place in solution or in the gas phase, where the reactants are evenly dispersed throughout a homogeneous mixture. However, for reactions in which one of the reactants is a pure solid or liquid (meaning that this reactant is not already mixed together with any other reactants), reactivity only occurs at the surface, where particles of the solid or liquid reactant come into contact with particles of the other reactants. All of the molecules or ions in the interior of the pure substance will not be colliding with the other necessary reactants, so they are not really contributing to the overall rate of the reaction. However, increasing the surface area will increase the frequency of potentially reactive collisions, because more reactant particles will be in contact with the other necessary reactants. and the situation: Mike was preparing for his chemistry exam. To see the chemistry concepts in practice he conducted two tests, test A and test B. In test A he used two liquid reactants evenly dispersed, but in test B he used one liquid reactant and one solid reactant. He was surprised to see that two tests had very different results. Answer the following question: In which test the reactants would have greater surface area to offer for reactions, test A or test B?
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The answer is:
test A

Problem: Given the question: Given the background: Allergy symptoms can range from mild to severe. Mild symptoms might include itchy eyes, sneezing, and a runny nose. Severe symptoms can cause difficulty breathing, which may be life threatening. Keep in mind that it is the immune system and not the allergen that causes the allergy symptoms. Allergy symptoms can be treated with medications such as antihistamines. Severe allergic reactions may require an injection of the hormone epinephrine. These treatments lessen or counter the immune system's response. and the situation: Robert studied two groups of patients. Group O had mild allergy symptoms, while group R displayed severe allergy symptoms. Answer the following question: Which group didn't experience sneezing?
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The answer is:
group R

Problem: Given the question: Given the background: However, when going across a period from left to right, the atomic radius actually tends to decrease. Why is this so? Each successive electron is going into the same principal energy level as the previous one, so the total amount of occupied space does not really go up significantly. Additionally, because protons are also added to the nucleus as you go across the row, the pull of the positively charged nucleus on the negatively charged electrons increases. This tighter pull leads to a slight decrease in atomic radius. As a result, the atomic radii of the elements exhibit a periodic trend, gradually tends to downward, but with a sharp spike up whenever electrons are added to a new principal energy level ( Figure below ). and the situation: There are two elements, Zaxon and Barton. Zaxon is an element that is further left on the period, and Barton is on the right of the period. Answer the following question: Which element has a weaker pull between the nucleus and the electron?
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The answer is:
Zaxon