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Kidney stones are a common ailment affecting approximately 10% of adults in the United States. They form when solutes precipitate out of solution as crystals in the urinary tract, and they can cause severe pain in the side, back, abdomen, and groin. Individuals who have been previously diagnosed with kidney stones have an increased probability of developing new stones relative to unaffected individuals. Different measures may help prevent the formation of different kinds of stones, so analysis of the composition of stones that have been passed or removed can aid in preventing recurrence. Stones can be ground into fine powders, dissolved in a small amount of solvent, and analyzed by infrared (IR) spectroscopy, as shown in Figure 1.
Figure 1 Schematic of kidney stone analysis by IR spectroscopyIR analysis of kidney stones from 50 individuals revealed the percentage of stones that contain each component, shown in Table 1 along with solubility data.Table 1 Kidney Stone Composition Parameters
Some studies indicate that potassium citrate, taken orally, may prevent the formation of calcium oxalate crystals, the most abundant component of kidney stones. Oxalic acid, shown in Figure 2, is significantly more soluble than calcium oxalate.
Figure 2 Structure of oxalic acid and its associated anions with increasing pHPotassium citrate alkalinizes the urine, potentially causing a decrease in oxalate solubility and the formation of more crystals. However, potassium citrate can also react with calcium oxalate according to the unbalanced equation shown in Reaction 1:CaC₂O₄ + K₃(C₆H₅O₇) → Ca₃(C₆H₅O₇) ₂ + K₂C₂O₄Reaction 1Calcium citrate and potassium oxalate are both hundreds of times more soluble than calcium oxalate, so the presence of citrate and potassium ions can help maintain calcium and oxalate ions in solution. This effect may be sufficient to overcome the decreased solubility that occurs at higher pH levels.
Adapted from Primiano A, Persichilli S, Gambaro G, et al. FT-IR analysis of urinary stones: a helpful tool for clinician comparison with the chemical spot test. Dis Markers. 2014;2014:176165.
-Consider the trends in atomic radii on the periodic table. The bond in citrate that is the longest and weakest with the lowest bond dissociation energy is the:

Question

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Kidney stones are a common ailment affecting approximately 10% of adults in the United States. They form when solutes precipitate out of solution as crystals in the urinary tract, and they can cause severe pain in the side, back, abdomen, and groin. Individuals who have been previously diagnosed with kidney stones have an increased probability of developing new stones relative to unaffected individuals. Different measures may help prevent the formation of different kinds of stones, so analysis of the composition of stones that have been passed or removed can aid in preventing recurrence. Stones can be ground into fine powders, dissolved in a small amount of solvent, and analyzed by infrared (IR) spectroscopy, as shown in Figure 1.

Figure 1 Schematic of kidney stone analysis by IR spectroscopyIR analysis of kidney stones from 50 individuals revealed the percentage of stones that contain each component, shown in Table 1 along with solubility data.Table 1 Kidney Stone Composition Parameters

Some studies indicate that potassium citrate, taken orally, may prevent the formation of calcium oxalate crystals, the most abundant component of kidney stones. Oxalic acid, shown in Figure 2, is significantly more soluble than calcium oxalate.

Figure 2 Structure of oxalic acid and its associated anions with increasing pHPotassium citrate alkalinizes the urine, potentially causing a decrease in oxalate solubility and the formation of more crystals. However, potassium citrate can also react with calcium oxalate according to the unbalanced equation shown in Reaction 1:CaC₂O₄ + K₃(C₆H₅O₇) → Ca₃(C₆H₅O₇) ₂ + K₂C₂O₄Reaction 1Calcium citrate and potassium oxalate are both hundreds of times more soluble than calcium oxalate, so the presence of citrate and potassium ions can help maintain calcium and oxalate ions in solution. This effect may be sufficient to overcome the decreased solubility that occurs at higher pH levels.
Adapted from Primiano A, Persichilli S, Gambaro G, et al. FT-IR analysis of urinary stones: a helpful tool for clinician comparison with the chemical spot test. Dis Markers. 2014;2014:176165.
-Consider the trends in atomic radii on the periodic table. The bond in citrate that is the longest and weakest with the lowest bond dissociation energy is the:

Quizplus · Accepted Answer

11ecba2d_11ba_0163_a3bf_35643a69c202_MD0008_00 Bond dissociation energy is the energy required to break a chemical bond; it is related to the bond length, or the distance between the nuclei of two bonded atoms. Shorter bonds are stronger and require more energy to break. Atoms with small atomic radii can form short, strong bonds whereas atoms with larger radii form longer, weaker bonds. Each subsequent row on the periodic table indicates an additional electron shell, and therefore a larger atomic radius, so atoms in the first row will have smaller atomic radii than atoms in the second row, and so on. Double bonds require more energy to break than single bonds. Citrate includes bonds between carbon and carbon, carbon and oxygen, carbon and hydrogen, and oxygen and hydrogen. Of the choices given, the C-C bond is the only single bond that does not involve a first row atom (hydrogen). Therefore, the C-C bond will be the longest and require the least energy to break. (Choices A and C) These options include hydrogen, which forms short, strong bonds. Note that although O-H bonds are commonly broken in acid-base reactions, these reactions also involve the formation of a new bond to hydrogen, which provides the high amount of energy necessary to break the old bond. (Choice B) C-O single bonds are of approximately the same strength as C-C single bonds. However, C=O double bonds are much shorter and stronger. Educational objective: The energy required to break a bond, known as the bond dissociation energy, is related to the bond length. Atoms with smaller radii (near the top of the periodic table) tend to form shorter, stronger bonds than atoms with larger radii.

Passage Kidney Stones Are a Common Ailment Affecting Approximately 10% of of Adults