Chem Ch 3

The smallest particle of of an element that retains the chemical properties of that element is a(n)?

Atom

The ancient Greek natural philosopher who first proposed the notion of the atom was

Democritus

The atomic mass of an atom of carbon is12 amu, and the atomic mass of an atom of oxygen is 16 amu. To produce CO2, 32 g of oxygen combine with 12 g of carbon. The ratio of the mass of oxygen in CO2 to the mass of oxygen in CO is

2:1

If two or more compounds are composed of elements A and B, the ratio of the masses of B combined with 1 g of A is always a ratio of small whole numbers. This statement is the law of

Law of Multi proportions

The number of protons in the nucleus of an element is called its

atomic #

Dalton's Atomic Theory helped to explain the law of conservation of mass because it stated that atoms

cannot be created or destroyed

To determine the mass in grams of an atom of any element, you would...

divide the mass of a mole of the element by Avogadro's number

The least massive particle in an atom is the

electron

According to the law of conservation of mass, when sodium, hydrogen, and oxygen react to form a compound, the mass of the compound will be...

equal to the sum of the masses of the reactants

The units of molar mass are

g/mol

Compared with a mole of lead atoms, a mole of iron atoms...

has the same number of atoms

According to the law of definite proportions, any two samples of KCI will have...

the same elements in the same proportions by mass

The average atomic mass of an element is...

the weighted average of all naturally occurring isotopes of the element

Carbon-14 has 8 neutrons. What is the atomic number of Carbon-14?

14-8=6

Oxygen has 3 naturally occurring isotopes in the following proportions: oxygen-16, 99.762% (15.99491 amu); oxygen-17, 0.038000% (16.99913 amu); oxygen-18, 0.20000% (17.99916 amu). Calculate the average atomic mass of oxygen.

15.9993001 amu

The atomic mass of Br is 79.9 amu. What is the mass of 2.0 mol of Br?

159.8 g

Which of the following statements are true?

*Atoms are mostly empty space *Almost all the mass in an atom is in the nucleus

What is molar mass? How is it related to atomic mass?

*Mass in grams of 1 mole of an atom of a pure substance *Equal to the average atomic mass, but has different # of atoms and label

How many moles of silver, Ag, are in a 35.65 g sample of Ag? (The molar mass of Ag is 107.9 g/mol)

0.3304 mol

The atomic mass of sulfur is 32.06 amu. How many atoms are present in exactly 2 mol of sulfur?

1.204x10^24 atoms

The mass of a sample of nickel (average atomic mass is 58.69 amu) is 11.74 g. How many atoms does it contain?

1.2x10^23

A neutral atom of Silicon-30 contains 14 protons. How many electrons does it have?

14+ + 14- = 0 charge

The average atomic mass of chromium is 52.00 amu. What is the mass of 3.00 mol of chromium?

3.00 x 52.00 = 156 g

The atomic number of nickel-60 is 28. How many neutrons does this isotope have?

32

An atom of potassium has 19 p+ and 20 n^0. Its mass number is

39

The atomic symbol for beryllium, 9/4/Be, indicates that the atomic number is

4 (bottom left of the element symbol)

How many moles are in a 63.60 g sample of carbon? (The molar mass of carbon is 12.01 g/mol)

5.3 mol

Which of the following is NOT equal to 1.00 mol of carbon-12?

6.0 g of Carbon

Rutherford's gold-foil experiment led him to conclude that...

a dense region of positive charge existed somewhere in the atom

Different atoms of the same element that have different masses are called

isotopes.

The total number of protons and neutrons in the nucleus of an isotope is called its

mass #

Neutral atoms of the same element can differ in

mass number

To calculate the number of atoms present in 2.0 mol of an element, you would...

multiply Avogadro's number of atoms per mole by 2.0 mol

The behavior of cathode rays in a glass tube containing gas at a low pressure led scientists to conclude that the rays are composed of

negative particles

Neutral atoms contain equal numbers of

protons and electrons

Protons are bound together by

strong nuclear forces

The molar mass of an element is numerically equal to...

the element's average atomic mass