CAS CH 101 Lecture Notes - Lecture 3: Molecular Mass, Horse Length, Unified Atomic Mass Unit

48 views2 pages

periwinklecat3

20 Sep 2015

School

Department

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

Well, 1u = 1/12 the mass of a 12c atom. Or, 12u = mass of one 12c atom. 1 u = (1/12) (12g 12c / na) = 1 / na. Na is avogadro"s number (6. 022 x 1023 atoms) Therefore, the answer for number of atoms is 39. 098u / na. Therefore, the average weight of any atom is the atomic mass (u) / na. Mass of na average atoms (found on the periodic table) Magnitude of average mass - no units. If with the label u, it is the mass of a single atom. If with the label g, it is the mass of a single mole. Expression: f6 (6. 015121) + f7 (7. 016003) = 0. 0750 (6. 015121) + 0. 9250 (7. 016003) Atomic mass unit (u): 1/12 mass of one 12c atom. Molar mass: mass in grams, equal to atomic weight. 1400u x (1atom / 238u) = 6 atoms. 4 moles (4 x avogadro"s number gives the number of atoms)

Related Questions

Place the elements in their proper position on the periodic table. To make this more challenging. I have not included their identities. Instead of the usual chemical symbol, each element is represented by a code letter. Some clues to the element's identities are listed below. In addition, the elements fall into these families or groups.

JKQ, WNVG, IAL, EPFZ, YBR, ODS, CXU, THM

Place each code letter in its proper space in the table below. Indicate the actual chemical symbol that corresponds to each letter.

V is an inert gas

E is an alkali metal

U is a halogen

D is in family VA

J is an alkaline earth metal

T is in family VIA

R has one less proton than A

A has six protons in its nucleus

R has an atomic number one more than J

O has an atomic number one more than A

S has 8 more protons in its nucleus than D

F has only one proton in each atom

Y has atoms that are larger than the atoms of B

I has the largest atomic number in its group

T is found in the fourth period

C has atoms that are larger than those of U, but smaller than those of X

V has one more proton in its nucleus that U

H has the smallest atomic number in its family

G has two protons in each atom

N is a third-period element

Q has an atomic mass greater than that of J and less than that of K

E has an atomic number less than that of Z, but greater than that of J

Z has more protons than other elements in its family

U is found in the second period

cyangnat561

There are two stable isotopes of supposium (Su). Su-191=190.9609u(27.30%) Su-194=193.9633 u(72.70%) Compute the atomic mass ofsupposium.
a. 194.0 u b. 193.1 u c. 191.8 u d. 190.9 u e. 192.5 u

Which would not be found with a mass spectrometer.
a. the atomic mass of a single isotope of potassium
b. the number of stable isotopes of potassium c.the mass of aproton
d. the number of protons in potassium e. the relative abundance oftwo isotopes of potassium

How many protons, neutrons, and electrons are in 24 Mg2+?
12
a. 10 protons, 12 electrons, 24 neutrons b. 12 protons, 10electrons, 12 neutrons
c.12 protons, 12 electrons, 24 neutrons d. 24 protons, 10electrons, 12 neutrons
e. 12 protons, 12 electrons, 12 neutrons

1.The age of rocks is sometimes calculated from the measured excessof lead 206 atoms over the normal abundance. The uranium isotopeU-238 decays to lead-206.What is the percent abundance of lead-206if there aare 4.52 X 10^21 atoms of lead-206 in a 198 g sample ofore that is 2.58% lead? a. 27.7 b. 0.0202 c. 4.70 x 10^-3 d. 30.4e. 0.782

2. The average atomic mass of B is 10.80 u. Boron has only twostable froms 10
5 B(10.00 u) and 11
5 B (11.00 u). What is the natural percent abundance of B?
a. 1.0% b. 20% c. 75% d. 3.8% e. 80%

3. 57.7 g Ni contains how many atoms? a. 3.47x10^23 b.0.983 c. 1.24x 10^24
d. 6.13x10^23 e. 5.92x10^23

4. What mass of magnesium is necessary to make 10.5 g of magnesiumbromide if 1.04 g of magnesium makes 7.88 g of magnesiumbromide?
a. 7.89 g b. 1.39 g c. 79.9 g d. 3.66 g e. 1.58 g

5. How many atoms of lead are required to cover a 33.0 cm by 45.0cm area witha sheet of lead that is 0.140 mm thick? The density oflead is 11.35 g/cm3.
a. 1.42x10^26
b. 2.29x10^25
c. 6.86x10^22
d. 2.29x10^26
e. 6.86X10^23

6. The natural abundance of calcium in the earth's crust is 3.4% bymass. How many calcium atoms are present in a 1.50 g sample of theearth's crust?
a. 7.7x10^22 b. 7.7x10^20 c. 3.1x 10^22 d.6.6x10^23 e.5.1x10^20

9.Rubidium possesses two stable forms and has an average mass of85.5. 85Rb has a mass of 84.9 and a percent abundance of 72.2%.What is the mass of the other form of Rb?

a. 85.7 u
b. 88.3 u
c. 86.1 u
d. 89.4 u
e. 87.1 u

10. Which is the more abundant isotope, CI-35 or CI37?
a. CI-17
b. CI-37
c. The two isotopes are equal in balance
d. CI-35
e. A third unstable isotope is more abundant

11. An element has 5 stable isotopes. The mass and percentage ofeach are:
69.9243 20.52%
71.9217 27.43%
72.9234 7.76%
73.9219 36.54%
75.9214 7.76%
The element is which of the following
a. Se b. Ge c. Ga d. As e. Zn

12. Lead-206 has a relative abundance of 23.6%. What sized block oflead (in cubic centimeters) will contain 8.34x10^21 atoms oflead-206? The density of lead is 11.35 is g/cm3.
a. 0.253
b. 0.0107
c. 1.07
d. 12.1
e. 0.330

13. When decomposed chemically, 73.0 grams of a sample of HCIproduce 71.0 g of Cl2 and 2.0 g of H2, while 34.0 g of a sample ofH2s produce 32.0g of S and 2.0g of H2. This is an example of theLaw:
a. of Definate Proportions
b. E=mc^2
c. of multiple proportions
d. of Conservation of Mass
e. none of these

CAS CH 101 Lecture Notes - Lecture 3: Molecular Mass, Horse Length, Unified Atomic Mass Unit

Document Summary

Get access

Related Documents

CAS CH 101 Lecture Notes - Lecture 2: Carbon-12

CAS CH 101 Lecture Notes - Lecture 2: Molar Mass, Dimensional Analysis, Avogadro Constant

CAS CH 101 Study Guide - Final Guide: Effective Nuclear Charge, Silver Nitrate, Ford F-Series

Related Questions