The number of Cu atoms in the wire may be conveniently derived from its mass by a two-step computation: first calculating the molar amount of Cu, and then using Avogadro’s number (NA) to convert this molar amount to number of Cu atoms: Considering that the provided sample mass (5.00 g) is a little less than one-tenth the mass of 1 mole of Cu (~64 g), a reasonable estimate for the number of atoms in the sample would be on the order of one-tenth NA, or approximately 1022 Cu atoms. It is usually expressed in atomic mass units (a.m.u.) Deriving the Number of Atoms and Molecules from the Mass of a Compound Because a proper formula is electrically neutral (with no net electrons gained or lost), the ions can be considered atoms for the purpose of calculating the formula mass. For either reactants or products, you will learn how to determine mass when given moles, moles when given mass and mass when given mass. One neurotransmitter that has been very extensively studied is dopamine, C8H11NO2. It is also important to understand the mechanism responsible for any changes in the number of neurotransmitter molecules released—for example, some dysfunction in exocytosis, a change in the number of vesicles in the neuron, or a change in the number of neurotransmitter molecules in each vesicle. (a) 0.819 g; (b) 307 g; (c) 0.23 g; (d) 1.235 × 106 g (1235 kg); (e) 765 g, 19. (b) 3.06 × 10−3 g of the amino acid glycine, C2H5NO2, (c) 25 lb of the herbicide Treflan, C13H16N2O4F (1 lb = 454 g), (d) 0.125 kg of the insecticide Paris Green, Cu4(AsO3)2(CH3CO2)2, (e) 325 mg of aspirin, C6H4(CO2H)(CO2CH3), (d) 78.452 g of aluminum sulfate, Al2(SO4)3. However, because a hydrogen peroxide molecule contains two oxygen atoms, as opposed to the water molecule, which has only one, the two substances exhibit very different properties. Check Your Learning The number of entities composing a mole has been experimentally determined to be 6.02214179 × 1023, a fundamental constant named Avogadro’s number (NA) or the Avogadro constant in honor of Italian scientist Amedeo Avogadro. Diamond is one form of elemental carbon. One important aspect of the complex processes related to dopamine signaling is the number of neurotransmitter molecules released during exocytosis. Key Concepts and Summary. Referring to the periodic table, the atomic mass of K is 39.10 amu, and so its molar mass is 39.10 g/mol. What is the mass of 0.443 mol of hydrazine, N2H4? The formula mass for an ionic compound is calculated in the same way as the formula mass for covalent compounds: by summing the average atomic masses of all the atoms in the compound’s formula. Which of the following represents the least number of molecules? Explain why. 7. Computing Molecular Mass for a Covalent Compound Analysis of these neurons from mice subjected to various drug therapies shows significant changes in the average number of dopamine molecules contained in individual vesicles, increasing or decreasing by up to three-fold, depending on the specific drug used. In an earlier chapter, we described the development of the atomic mass unit, the concept of average atomic masses, and the use of chemical formulas to represent the elemental makeup of substances. For example, Dalton’s atomic theory was an attempt to explain the results of measurements that allowed him to calculate the relative masses of elements combined in various compounds. Great progress has been made in brain research over the past few decades, and the BRAIN Initiative, a federal initiative announced in 2013, aims to accelerate and capitalize on these advances through the concerted efforts of various industrial, academic, and government agencies (more details available at www.whitehouse.gov/share/brain-initiative). The recommended daily dietary allowance of vitamin C for children aged 4–8 years is 1.42 × 10−4 mol. The appearance of copper sulphate hydrates is bright blue in colour. What is the molecular mass (amu) for this compound? Moreover, the mass of an electron is negligibly small with respect to the mass of a typical atom. The link between the mass of an element and the number of atoms it contains is the relative atomic mass of the element. Ibuprofen, C13H18O2, is a covalent compound and the active ingredient in several popular nonprescription pain medications, such as Advil and Motrin. The formula mass of a covalent compound is also called the molecular mass. Molecules of this compound are comprised of 13 carbon atoms, 18 hydrogen atoms, and 2 oxygen atoms. 9. Today, we possess sophisticated instruments that allow the direct measurement of these defining microscopic traits; however, the same traits were originally derived from the measurement of macroscopic properties (the masses and volumes of bulk quantities of matter) using relatively simple tools (balances and volumetric glassware). Dysfunctions in the dopamine systems of the brain underlie serious neurological diseases such as Parkinson’s and schizophrenia. It sends and receives signals to and from muscles and other internal organs to monitor and control their functions; it processes stimuli detected by sensory organs to guide interactions with the external world; and it houses the complex physiological processes that give rise to our intellect and emotions. This is the mass of the atom of a specific element. AlPO4: 1.000 mol Calculate the molar mass of each of the following compounds: Calculate the molar mass of each of the following: Calculate the empirical or molecular formula mass and the molar mass of each of the following minerals: Determine the number of moles of compound and the number of moles of each type of atom in each of the following: Determine the mass of each of the following: Determine the number of moles of the compound and determine the number of moles of each type of atom in each of the following: The approximate minimum daily dietary requirement of the amino acid leucine, C. Determine the mass in grams of each of the following: Determine the number of atoms and the mass of zirconium, silicon, and oxygen found in 0.3384 mol of zircon, ZrSiO, Determine which of the following contains the greatest mass of hydrogen: 1 mol of CH, Determine which of the following contains the greatest mass of aluminum: 122 g of AlPO. These neurotransmitter molecules are stored in small intracellular structures called vesicles that fuse to the cell wall and then break open to release their contents when the neuron is appropriately stimulated. Its formula has twice as many oxygen atoms as the other two compounds (one each). One 55-gram serving of a particular cereal supplies 270 mg of sodium, 11% of the recommended daily allowance. Acetaminophen, C8H9NO2, is a covalent compound and the active ingredient in several popular nonprescription pain medications, such as Tylenol. What is the mass of 2.561 mol of gold? A certain nut crunch cereal contains 11.0 grams of sugar (sucrose, C, A tube of toothpaste contains 0.76 g of sodium monofluorophosphate (Na. The relative formula mass (aka the formula weight) is the sum of the atomic weights (not average atomic masses) of the atoms in the formula of a compound. The broad field of neuroscience spans all aspects of the structure and function of the central nervous system, including research on the anatomy and physiology of the brain. It is calculated using the unit “amu” (atomic mass units). Subscribe to get latest content in your inbox. (a) 56.107 amu; (b) 54.091 amu; (c) 199.9976 amu; (d) 97.9950 amu. Deriving Moles from Grams for an Element Consistent with its definition as an amount unit, 1 mole of any element contains the same number of atoms as 1 mole of any other element. Formula mass is the sum of the masses of the atoms present in the empirical formula. (a) 197.382 g mol−1; (b) 257.163 g mol−1; (c) 194.193 g mol−1; (d) 60.056 g mol−1; (e) 306.464 g mol−1, 17. Deriving Moles from Grams for a Compound The formula mass of copper sulphate is calculated in the below table. Beryllium is a light metal used to fabricate transparent X-ray windows for medical imaging instruments. The masses of 1 mole of different elements, however, are different, since the masses of the individual atoms are drastically different. The Cullinan diamond was the largest natural diamond ever found (January 25, 1905). How to calculate the formula mass and molar mass of a compound. 5H2O. Solution The relative atomic mass scale is used to compare the masses of different atoms. Computing Formula Mass for an Ionic Compound A mole is defined as the amount of substance containing the same number of discrete entities (such as atoms, molecules, and ions) as the number of atoms in a sample of pure 12C weighing exactly 12 g. One Latin connotation for the word “mole” is “large mass” or “bulk,” which is consistent with its use as the name for this unit. This approach is perfectly acceptable when computing the formula mass of an ionic compound. The formula does not consider the internal shell structure of the nucleus. Copper is commonly used to fabricate electrical wire (Figure 7). 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