Chapter 3 packet Review Questions and answers
1.) Define:
a.) The Law of definite proportions
A pure compound, whatever its source, always contains definite or constant proportions of the elements by mass.
b.) The Law of multiple proportions
When two elements form more than one compound, the masses of one element in these compounds for a fixed mass of the other element are in rations of small whole numbers.
2.) 2.00 g of element x combine with 5.00 g of element Y. How many grams of element Y combines with 5.00 g of element X?
12.5 g of element x
3.) What is the general name for an isotope of any element?
Nuclide
4.) How does an isotope of an element differ from the normal atoms of that element?
The numbers of neutrons in the atom are different.
5.) What do you call the total number of protons and neutrons in the nucleus of a atom?
Atomic Mass.
6.) How many moles of hydrogen atoms are in 4.63 g of Ca(OH)2?
0.125 mols
7.) Which of the following has the greatest total number of atoms; 5.00g of Na, 1.04X10^23 molecules of O2, or 0.74 moles of I2?
0.74 moles of I2.
8.) How much Mg contains the same number of atoms as 12.29 g of Ni?
4.8155 g of Mg.
9.) How many moles are in 31.4 g of BaCl2?
0.151 mol of BaCl2.
10.) Describe the outcome of each experiment and how it was found:
a.) J.J. Thomson’s cathode ray experiment.
Supported the existence of cathode rays and a negative charged object. Also, he calculated the charge to mass ratio for the electron.
b.) Miliken and the oil drop experiment.
He was able to determine the electron’s charge.
c.) Rutherford’s gold foil experiment.
Rutherford bombarded a gold foil with positive charged alpha particles. He discovered that although most particles passed through, some deflected back. He concluded that most of the space in an atom is empty and there is a small positively charged nucleus in the center.
d.) Chadwick’s experiment with Beryllium atoms.
He discovered that by bombarding beryllium atoms with alpha particles, the beams produced were not deflected by electrical field. This meant that a neutral particle existed. He named it the neutron.
11.) Contrast the differences between the Plum Pudding model, Bohr’s model, and the Schrodinger wave mechanical model.
Plum Pudding – negatively charged electrons are embedded in a positively charged cloud.
Bohr – energy of orbits are quantized. The orbits closets to the nucleus have the least energy and the furthest would have the most. However, it could only explain hydrogen.
Schrodinger – electrons, neutrons, and protons. Protons and neutrons are in the nucleus and electrons orbit the nucleus in an electron cloud.
12.)What are nuclear forces?
The short-range forces acting on protons and neutrons in atomic nuclei. Two types actually exist, the "strong force" which holds nuclei together, and the "weak force" which determines the ratio between the numbers of protons and neutrons.
13.)In order from the greatest amount of mass to the least, what is the correct order of the three particles in an atom.
Neutron, Proton, Electron.
14.) Calculate the atomic mass of Uranium give the following data:
238.158
15.) How many atoms are in 4.00 g of sulfur?
7.50X10^22 atoms
16.) How many moles of O2 are there in 50.0 g of O2?
1.56 mols
17.)What are isotopes? Show the number of e,p, and n in C-12 and C-14 and write the symbols for them.
Isotopes are atoms with different numbers of neutrons.
C-12 – 6e, 6p, 6n
C-14 – 6e, 6p, 8n
18.) What forces keep the nucleus from falling apart?
Nuclear forces.
19.) Do 1.0 g of Al and 1.0 g of Fe contain the same number of atoms? Explain.
No because of different atomic masses, therefore different # of moles and different # of atoms.
20.)
21.)grams, the molar mass can be found by adding together the atomic masses of each separate element in the component.