Definitions
What is an isotope?
Two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons
A positively charged particle found in the nucleus:
a. is called a(n) _____________
b. has a relative mass of ___________
a. proton.
b. 1.
Give the number of Protons, Neutrons, and Electrons for neutral Silver-109
Protons: 47
Neutrons: 109-47 = 62
Electrons: 47
Ibuprofen, C13H18O2, that is manufactured in Michigan contains 75.69% by mass carbon, 8.80% hydrogen, and 15.51% oxygen. If you buy some ibuprofen for a headache while you are on vacation in Germany, what law states that it has the same percentage composition as the ibuprofen you buy at home?
Law of Definite Proportions
How many particles are in
a. 1 mol of carbon?
b. 1 mol of lithium?
c. 1 mol of eggs?
d. Will 1 mol of each of these substances have the same mass?
a - c. There are 6.022 X 10^23 particles in 1 mol of each of these substances.
d. One mole of one substance will not necessarily have the same mass as one mole of another substance.
Explain the difference between the mass number and the atomic number of a nuclide.
Mass number is the total number of protons and neutrons in the nucleus of an isotope.
Atomic number is the total number of protons in the nucleus of each atom of an element.
A negatively charged particle found in the nucleus:
a. is called a(n) _____________
b. has a relative mass of ___________
a. electron.
b. 0.
The element boron, B, has an atomic mass of 10.81u according to the periodic table. However, no single atom of boron has a mass of exactly 10.81u. How can you explain this difference?
The periodic table reports the average atomic mass, which is a weighted average of
all isotopes of boron.
CH4 + O2 --> CO2 + 2H2O
If 16g of CH4 reacts with 64g of O2, producing 44g of CO2, how many grams of water are produced?
(16+64)-(44)=36g
What is the mass in grams of 2.000 mol of oxygen atoms?
32.00 g
Define Avogadro's Number:
- what is the number?
- what does it mean?
6.022 X 10^23
It is the number in one mole of any substance.
A neutral charged particle found in the nucleus:
a. is called a(n) _____________
b. has a relative mass of ___________
a. neutron
b. 1.
Why is it necessary to use the average atomic mass of all isotopes, rather than the mass of the most commonly occurring isotope, when referring to the atomic mass of an element?
Elements rarely occur as only one isotope; rather, they exist as mixtures of different isotopes of various masses. Using a weighted average atomic mass, you can account for the less common isotopes.
A sample of baking soda, NaHCO3, ALWAYS contains 27.37% by mass of sodium, 1.20% of hydrogen, 14.30% of carbon, and 57.14% of oxygen.
If you have 100.0g of NaHCO3,
a. how many grams of Sodium are in the baking soda?
b. how many grams of Hydrogen are in the baking soda?
c. What law is used to determine this?
a. 27.37g of Sodium
b. 1.20g of Hydrogen
c. Law of Definite Proportions.
How many moles of aluminum exist in 100.0 g of aluminum?
3.706 mol
What is the word for a specific isotope?
nuclide
Tell where the following are located in the atom:
a. proton
b. neutron
c. electron
a. nucleus
b. nucleus
c. electron cloud
A certain element exists as three natural isotopes, as shown in the table below.
Isotope. Mass (amu). Percent natural abundance
1. 19.99244 90.51%
2. 20.99395 0.27%
3. 21.99138 9.22%
Calculate the average atomic mass of this element.
20 amu
If 3 g of element C combine with 8 g of element D to form compound CD, how many grams of D are needed to form compound CD2?
16g. Since you would have 8g for CD, you would need 8X2 if it is CD2
How many atoms are there in 2.50 mol of uranium?
1.51 X 10^24 atoms
What is the definition of amu?
a. 1 amu = the mass of 1/12 of one carbon-12 atom
What particle of the atom occupies the largest space and where does it reside?
The electron, which resides in the electron cloud.
Calculate the average atomic mass of lithium, which occurs as two isotopes that have the following atomic masses and abundances in nature: 6.017 amu, 7.30% and 7.018 amu, 92.70%.
6.94 amu
Glucose (C6H12O6) is always made up of 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms.
If we have 108.099 g of Carbon, and we produce 270.234g of Glucose, with no byproducts left over, how much Hydrogen and Oxygen will be required?
72.066 *1.500 = 108.099g of Carbon
180.156*1.500 = 270.234 g of Glucose
Therefore, we would need:
12.096*1.5000 = 18.144 g of Hydrogen
95.994*1.5000 = 143.991 g of Oxygen
How many atoms are in 80.45 g of magnesium?
1.994 X 10^24 atoms