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Q: A lewis acid is a substance that accepts a pair of electrons to form what? Read this paragraph and choose the correct option from the provided answers: Gilbert Lewis (1875-1946) proposed a third theory of acids and bases that is even more general than either the Arrhenius or Brnsted-Lowry theories. A Lewis acid is a substance that accepts a pair of electrons to form a covalent bond. A Lewis base is a substance that donates a pair of electrons to form a covalent bond. So, a Lewis acid-base reaction is represented by the transfer of a pair of electrons from a base to an acid. A hydrogen ion, which lacks any electrons, accepts a pair of electrons. It is an acid under both the Brnsted-Lowry and Lewis definitions. Ammonia consists of a nitrogen atom as the central atom with a lone pair of electrons. The reaction between ammonia and the hydrogen ion can be depicted as shown in the Figure below . Choices: - accretion bond - functionality bond - ambivalent bond - covalent bond A:
(Answer)
covalent bond

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Q: Elongation is the addition of what to the mrna strand? Read this paragraph and choose the correct option from the provided answers: Elongation is the addition of nucleotides to the mRNA strand. Choices: - codons - glycine - filaments - nucleotides A:
(Answer)
nucleotides

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Q: Unevenness or asymmetry in the focus of the eye describes what visual defect? Read this paragraph and choose the correct option from the provided answers: Another common vision defect is astigmatism, an unevenness or asymmetry in the focus of the eye. For example, rays passing through a vertical region of the eye may focus closer than rays passing through a horizontal region, resulting in the image appearing elongated. This is mostly due to irregularities in the shape of the cornea but can also be due to lens irregularities or unevenness in the retina. Because of these irregularities, different parts of the lens system produce images at different locations. The eye-brain system can compensate for some of these irregularities, but they generally manifest themselves as less distinct vision or sharper images along certain axes. Figure 26.8 shows a chart used to detect astigmatism. Astigmatism can be at least partially corrected with a spectacle having the opposite irregularity of the eye. If an eyeglass prescription has a cylindrical correction, it is there to correct astigmatism. The normal corrections for short- or farsightedness are spherical corrections, uniform along all axes. Choices: - presbyopia - hyperopia - myopia - astigmatism A:
(Answer)
astigmatism