Avogadro's number, calculated from the atomic weight of hydrogen, tells us how many atoms or molecules are in a mole
The resulting base for all calculations of moles and molarity (how many molecules are present when you weigh out a substance or measure from a stock solution) is the following:
1 g of hydrogen atoms = 6 × 1023 hydrogen atoms = 1 mole of hydrogen
Sulfur has a molecular weight of 32. How many moles and atoms are there in 120 grams of sulfur?
(a) 3.75 and 6 × 1023
(b) 32 and 6 × 1023
(c) 1.75 and 1.05 ×1024
(d) 3.75 and 2.25 × 1024
(d)
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You are at the aquarium looking at a freshwater mammal tank and a manatee swims close to the glass. On his front flippers you see fingernails. You think, what possible use could fingernails be to a manatee, then you realize they are of no use at all. Which of the following best explains the presence of fingernails on a manatee?
A. they are remnants of the bones used by fish for their fins. B. they are homologous structures. C. the bones are protruding from the fins and only look like fingernails, even though every manatee in the tank looks like it has fingernails. D. convergent evolution has occurred. E. they are vestigial structures.
Morphological traits are commonly used to identify species, which of the following can also be used?
A. The ability to interbreed. B. Molecular similarity (DNA and chromosome comparisons). C. Ecological factors. D. Evolutionary relationships. E. All of these.
When an enzyme-catalyzed reaction reaches equilibrium ____
a. the enzymes are now inhibited b. the chemical reactions cease c. the rate of the forward and reverse reactions are equal d. the concentration of reactants equals the concentration of products e. ATP is no longer required to drive the reaction
Stroke is an interruption of blood flow to the lungs, which must have about 15% of the heart's output at rest.
a. true b. false