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Ch.3 - Molecules and Compounds
Tro - Chemistry: A Molecular Approach 5th Edition
Tro5th EditionChemistry: A Molecular ApproachISBN: 9780134874371Not the one you use?Change textbook
All textbooksTro 5th EditionCh.3 - Molecules and CompoundsProblem 60a
Chapter 3, Problem 60a

Calculate the formula mass for each compound. a. MgBr2 b. HNO2 c. CBr4 d. Ca(NO3)2

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Step 1: Identify the atomic masses of the elements in the compound. The atomic mass of Magnesium (Mg) is approximately 24.305 g/mol and the atomic mass of Bromine (Br) is approximately 79.904 g/mol.
Step 2: Determine the number of each type of atom in the compound. In MgBr2, there is one atom of Magnesium and two atoms of Bromine.
Step 3: Multiply the atomic mass of each element by the number of atoms of that element in the compound. For Magnesium, this would be 24.305 g/mol * 1 = 24.305 g/mol. For Bromine, this would be 79.904 g/mol * 2 = 159.808 g/mol.
Step 4: Add up the results from step 3 to find the formula mass of the compound. The formula mass of MgBr2 would be the sum of the mass of Magnesium and the mass of Bromine, which is 24.305 g/mol + 159.808 g/mol.
Step 5: The formula mass of MgBr2 is the result from step 4. This is the final answer.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all the atoms in a chemical formula. For example, in magnesium bromide (MgBr2), the molar mass is determined by adding the atomic mass of magnesium (24.31 g/mol) to twice the atomic mass of bromine (79.90 g/mol).
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Periodic Table

The periodic table is a tabular arrangement of chemical elements, organized by increasing atomic number. Each element's atomic mass is listed, which is essential for calculating molar mass. Understanding the periodic table allows students to quickly find the necessary atomic masses for elements like magnesium and bromine when determining the formula mass of compounds.
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Periodic Table Classifications

Chemical Formula

A chemical formula represents the composition of a compound, indicating the types and numbers of atoms present. In the case of MgBr2, the formula indicates one magnesium atom and two bromine atoms. This information is crucial for calculating the formula mass, as it dictates how many times to include each element's atomic mass in the total calculation.
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