Chem 2045 Exam 1 (Ch.1-3) Flashcards
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Questions and Answers

What is the molar mass of Ba3(PO4)2 if Ba = 137.3, P = 30.97, O = 16?

601.84

How many moles of Ba3(PO4)2 are in 60.0 grams of Ba3(PO4)2?

0.0997 mol

How many moles of O are present in the same sample as question 2?

0.7976 mol

How many oxygen atoms are in question 3?

<p>4.803x10^23</p> Signup and view all the answers

What is the mass composition of O in Ba3(PO4)2?

<p>21.27%</p> Signup and view all the answers

How do you calculate empirical formula for a compound based on elemental mass compositions?

<p>Convert mass to moles, write pseudoformula, divide by smallest subscript and clear fractions.</p> Signup and view all the answers

What is the empirical formula for a compound based on the following elemental mass compositions: C 49.48%, H 5.19%, N 28.85%, O 16.48%?

<p>C4H5N2O</p> Signup and view all the answers

How do you calculate molecular formula?

<p>Find empirical formula, find n (n = molar mass / empirical formula molar mass), multiply n by empirical formula subscripts.</p> Signup and view all the answers

If the molar mass in slide 7 is 194.19 grams, what is the molecular formula?

<p>C8H10N4O2</p> Signup and view all the answers

What does Rutherford's Theory state?

<p>Protons are positive charge, neutrons are neutral, electrons are negative charge.</p> Signup and view all the answers

What is atomic number (Z)?

<p>Number of protons</p> Signup and view all the answers

What is mass number (A)?

<p>Number of protons + number of neutrons</p> Signup and view all the answers

What is the formula for the number of protons?

<p>A - Z</p> Signup and view all the answers

What is an isotope?

<p>Atoms with the same number of protons but different number of neutrons</p> Signup and view all the answers

What is the atomic mass formula for isotopes?

<p>(fraction of iso. 1 x mass of iso 1) + (fract. of iso. 2 x mass of iso. 2) + ...</p> Signup and view all the answers

What is an example of an atomic mass problem involving boron?

<p>10.8 amu</p> Signup and view all the answers

What is an element?

<p>Substance composed of a single type of atom</p> Signup and view all the answers

What is a compound?

<p>Substance composed of two or more elements in a fixed, definite proportion</p> Signup and view all the answers

How are compounds held together?

<p>Chemical bonds, which result from attractions between charged particles.</p> Signup and view all the answers

What is a chemical formula?

<p>It indicates the elements present in the compound and the relative number of atoms or ions of each.</p> Signup and view all the answers

What is the name for an element that exists as a molecule?

<p>Diatomic molecule</p> Signup and view all the answers

What are the names of elemental groups?

<p>Inner Transition metals: Lanthanides, Actinides; Main Table: Alkali metals, Alkaline earth metals, Halogens, Noble Gases.</p> Signup and view all the answers

What are the types of ions?

<p>Cations and Anions</p> Signup and view all the answers

How do electrons in an atom make chemical bonds?

<p>Like charges repel and opposite charges attract.</p> Signup and view all the answers

What are the two types of chemical bonds?

<p>Ionic and covalent</p> Signup and view all the answers

What is an ionic bond?

<p>The transfer of electrons from a metal to a nonmetal.</p> Signup and view all the answers

What is a covalent bond?

<p>The sharing of electrons between two nonmetals.</p> Signup and view all the answers

What are atomic elements vs molecular elements?

<p>Atomic elements exist as single atoms, while molecular elements exist as bonded pairs or groups of atoms.</p> Signup and view all the answers

What are the bonds of molecular compounds?

<p>Usually composed of two or more covalently bonded nonmetals.</p> Signup and view all the answers

What are the bonds of ionic compounds?

<p>Composed of cations and anions bound together by ionic bonds.</p> Signup and view all the answers

What is an example of a polyatomic ion?

<p>ClO− and HCO3−</p> Signup and view all the answers

What are the properties of ionic compounds?

<p>Typically solids with high melting points, non-conductive in solid form, conductive in molten form.</p> Signup and view all the answers

What are the steps to write an ionic compound formula?

<p>Positive and negative charges must balance, and the formula reflects the smallest whole-number ratio.</p> Signup and view all the answers

What are basic polyatomic ions to memorize?

<p>NH4+, CO32−, CH3COO−, HCO3−, OH−, PO43−, NO3−, ClO3−, NO2−, ClO4−, MnO4−, SO42−, Cr2O72−, SO32−.</p> Signup and view all the answers

What are the types of ionic compounds?

<p>Binary ionic compounds and polyatomic ionic compounds.</p> Signup and view all the answers

How do you name binary compounds?

<p>The first element is named as is, and the second element gets the -ide suffix.</p> Signup and view all the answers

What are basic monoatomic ions to memorize?

<p>Fluorine F−, Chlorine Cl−, Bromine Br−, Iodine I−, Oxygen O2−, Sulfur S2−, Nitrogen N3−, Phosphorus P3−.</p> Signup and view all the answers

How do you name ionic compounds with polyatomic ions?

<p>Use the name of the polyatomic ion whenever it occurs in the formula.</p> Signup and view all the answers

What is a molecular compound?

<p>Compounds composed of two or more covalently bonded nonmetals.</p> Signup and view all the answers

How do you name molecular compounds?

<p>Use prefixes for both nonmetals and change the second nonmetal's suffix to -ide.</p> Signup and view all the answers

What is formula mass?

<p>The sum of the atomic masses of all the atoms in the chemical formula of a molecule.</p> Signup and view all the answers

How do you calculate formula mass?

<p>By summing the products of the number of atoms of each element and their respective atomic masses.</p> Signup and view all the answers

What is a mole?

<p>The amount of material containing $6.022 × 10^{23}$ particles.</p> Signup and view all the answers

How do you convert between number of particles and mass?

<p>Using molar mass in combination with Avogadro's number.</p> Signup and view all the answers

What do subscripts in a formula indicate?

<p>The number of atoms of each type of element in a compound.</p> Signup and view all the answers

What is an example of moles in a chemical formula?

<p>1 mole of PBr3 contains 1 mole P and 3 moles Br.</p> Signup and view all the answers

What is mass percent composition?

<p>The percentage by mass of each element in the compound.</p> Signup and view all the answers

What is an example of mass percent composition?

<p>25% H and 75% C in a 10.0 g sample.</p> Signup and view all the answers

What is the formula for mass percent composition?

<p>(mass of an element / total mass of the compound) x 100%</p> Signup and view all the answers

How can percent composition of a compound be calculated?

<p>(mass of A in 1 mol of compound / molar mass of compound) x 100%</p> Signup and view all the answers

What is a solution?

<p>A homogeneous mixture of two or more substances.</p> Signup and view all the answers

What is a solvent?

<p>The solution component that is higher relative to other components.</p> Signup and view all the answers

What is a solute?

<p>The solution component present in a concentration less than that of the solvent.</p> Signup and view all the answers

What is an aqueous solution?

<p>A solution for which water is the solvent.</p> Signup and view all the answers

What is molarity?

<p>Unit of concentration, defined as moles of solute per liter of solution.</p> Signup and view all the answers

What is the molarity (M) formula?

<p>(amount of solute in mols / volume of solution in L)</p> Signup and view all the answers

What is dilution?

<p>The process whereby the concentration of a solution is reduced by adding solvent.</p> Signup and view all the answers

What is the molarity formula for dilution?

<p>M1V1 = M2V2</p> Signup and view all the answers

Study Notes

Molar Mass and Mole Calculations

  • Molar mass of Ba3(PO4)2 is 601.84 g/mol, calculated using individual atomic masses.
  • 60.0 grams of Ba3(PO4)2 equates to 0.0997 moles using the formula: grams x (1 mol/molar mass).
  • Amount of oxygen in 0.0997 moles of Ba3(PO4)2 is 0.7976 moles, calculated using the ratio of oxygen in the compound.

Avogadro's Number and Atoms

  • Number of oxygen atoms in 0.7976 moles is 4.803 x 10^23, determined using Avogadro's number.
  • Avogadro's number (6.022 x 10^23) indicates the quantity in one mole of any element.

Mass Composition and Empirical Formulas

  • Mass composition of oxygen in Ba3(PO4)2 is 21.27%, found by dividing mass of oxygen by total molar mass and multiplying by 100%.
  • To find an empirical formula from mass compositions: convert mass to moles, write a pseudoformula, and simplify by dividing by the smallest subscript.

Molecular Formulas

  • The molecular formula is derived from the empirical formula and molar mass using the relationship n = molar mass/empirical formula mass.
  • Given a molar mass of 194.19 grams and an empirical formula mass of 97.1, the molecular formula is C8H10N4O2.

Atomic Structure

  • Rutherford's theory describes protons (positive), neutrons (neutral in nucleus), and electrons (negative, in empty space).
  • Atomic number (Z) indicates the number of protons, defining the element; mass number (A) is the total of protons and neutrons.

Isotopes and Atomic Mass

  • Isotopes have the same number of protons but different neutrons, resulting in different masses but similar chemical behaviors.
  • Atomic mass is calculated as a weighted average of isotopic masses based on their natural abundance.

Chemical Bonds and Compounds

  • Compounds consist of two or more elements bonded chemically through ionic or covalent bonds.
  • Ionic bonds involve electron transfer between metals (cations) and nonmetals (anions), while covalent bonds involve electron sharing between nonmetals.

Types of Elements

  • Atomic elements consist of single atoms (e.g., He, Na), while molecular elements consist of bonded atoms (e.g., diatomic H2, O2).

Ionic and Molecular Compounds

  • Ionic compounds consist of cations and anions creating a formula unit, while molecular compounds consist of covalently bonded nonmetals forming molecules.
  • Naming conventions differ: binary ionic compounds are named with -ide endings for anions; polyatomic ions maintain their names.

Percent Composition and Solutions

  • Mass percent composition is the percentage by mass of each element in a compound, calculated as (mass of element/total mass) x 100%.
  • Solutions consist of a solute (lesser amount) dissolved in a solvent (greater amount), often water in aqueous solutions.

Molarity and Dilutions

  • Molarity (M) is a concentration unit defined as moles of solute per liter of solution, calculated using M = (amount of solute in mols/volume of solution in L).
  • The dilution equation M1V1 = M2V2 allows for the calculation of molarity in diluted solutions.

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Test your knowledge with these flashcards for Chem 2045 Exam 1, covering key concepts from Chapters 1 to 3. Topics include molar mass calculations and moles in chemical compounds. Perfect for reviewing essential chemistry concepts before your exam.

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