7/27/2019 Chapter 0211 With Answers http://slidepdf.com/reader/full/chapter-0211-with-answers 1/17 Quizzes and Exams • Please write in non-erasable blue or black pen , no pencil! (Will lose 1 point for pencil or erasable ink) • I will put periodic table on backs of quizzes, if you need them. • BOX answers! If it’s not obvious where (or which) the answer is that I’m supposed to grade, it will get no credit.• Remember to bring your non-programmable calculators to class on Wednesdays. • Make sure your answers make sense (can there be 23 grams of zinc in a 4.75 g sample of zinc oxide?). • You may only use approved calculators on quizzes; others will be confiscated for the duration of the quiz or exam.
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1. Dalton’s Atomic Theory is based on empirical observations, formulated
as Laws of
Conservation of Mass
Definite Proportions
Multiple Proportions
No detectable gain or loss of mass occurs in chemical reactions.
In a compound, elements are always combined in the same proportion by mass.
Whenever two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio
of small whole numbers.
2. Summary of Dalton’s Theory
--Matter consists of tiny particles called atoms.
--Atoms are indestructible. In chemical reactions, the atoms rearrange but they do not
themselves break apart.
--In any sample of a pure element, all the atoms are identical in mass and other properties.
--The atoms of different elements differ in mass and other properties.
--In a given compound the constituent atoms are always present in the same fixednumerical ratio.
1. In a class A is worth 4 points and B is worth 3. Out of 20 grades, if you
have 4 A’s (20%) and 16 B’s (80%), what is your average?
If an element has two isotopes, A (Z = 4 amu) and B (Z = 3 amu), and their natural abundance is 20% A and 80% B, what is the average molecular
weight?
2. Naturally occurring boron (Z = 10.8110 amu) is composed of two isotopes,10B and 11B. Atoms of 10B have a mass of 10.0129 amu and those of 11B have a mass of 11.0093 amu. Calculate the percentages by mass
1. In a class A is worth 4 points and B is worth 3. Out of 20 grades, if you
have 4 A’s (20%) and 16 B’s (80%), what is your average?
If an element has two isotopes, A (Z = 4 amu) and B (Z = 3 amu), and their natural abundance is 20% A and 80% B, what is the average molecular
weight?
Answer: Grade average = 3.2 points
Average molecular weight = 3.2 amu
2. Naturally occurring boron (Z = 10.8110 amu) is composed of two isotopes,10B and 11B. Atoms of 10B have a mass of 10.0129 amu and those of 11B have a mass of 11.0093 amu. Calculate the percentages by mass