Make Sure to Use the Correct Number of Significant Figures and Show All Your Work!

Chem101 NSCC Exam #1 Name______100pts

Make sure to use the correct number of significant figures and show all your work!

69 71 1. (4pts) Two isotopes of gallium (Ga) are naturally occurring with Ga at 60.1% and Ga at 39.9%. What is the atomic mass of gallium?

6 0 . 1  6 9 a m u  4 1 . 4 7 a m u 1 0 0 3 9 . 9  7 1 a m u  2 8 . 3 3 a m u 1 0 0 4 1 . 4 7  2 8 . 3 3  6 9 . 8 a m u

2. (16pts – 4pts each)Carry out the conversions below. You can use the charts provided to get the proper conversion factors.

a. How many miles are there in 3.01km?

0.621miles 3.01km   1.87miles 1km

b. In a 6-ft tall person, the femur might be 19.5 in long. What is the length of that person’s femur in millimeters?

2.54cm 10mm 19.5in    495mm 1inch 1cm

c. The density of lead is 11.3g/mL. The water level in a graduated cylinder initially at 215mL rises to 285mL after a piece of lead is submerged. What is the mass in grams of lead? Subtraction (significant out to the ones place) 2 8 5 m L  2 1 5 m L  7 0 . m l 1 1 . 3 g 7 0 . m l   7 9 0 g 1 m L

d. A hummingbird has a mass of 0.0055kg. What is the mass of the hummingbird in grams?

1 0 0 0 g 0 . 0 0 5 5 k g   5 . 5 g 1 k g

3. a. (2pts) Which element has three 2p electrons?___N_____

b. (2pts) Which element has 6 electrons in shell 3?__S___ 4. (6pts) Circle the numbers below which are not written in proper scientific notation. Also, depict all the numbers as ‘standard numbers.

Standard Number 1.605 x 10-5 0.00001605 0.11 x 104 1100 1.400 x 103 1400. 403.15 x 10-2 4.0315

5. (6pts) Describe the atoms below in terms of number of protons, neutrons, and electrons. Fill in the missing information.

42 15 3- 7 N Protons___7_____ 20 Ca Protons___20___ Neutrons__8_____ Neutrons__22__ Electrons__10____ Electrons__20___

6. (6pts) Fill in the symbols or names for the following elements.

Beryllium _oxygen____ Lithium

__Be____ O __Li___

7. (16pts) Write the electronic configuration for each atom listed below. For each atom state how many valence electrons it has. Circle the atom(s) that have a ‘filled shell’.

Electronic configuration # of valence of electrons

O 1s22s22p4 6 Mg2+ 1s22s22p6 8 (I threw this valence ques. out because it’s confusing) Cl 1s22s22p63s23p5 7 Ge 1s22s22p63s23p64s23d104p2 4

8. (12pts) Draw the Lewis dot structures for:

2- NCl3 CO3 HCN (C is in the middle)

O Cl N O C Cl Cl O H C N 9. (8pts) Name or write the formula for the following: Name Formula

a. ___Magnesium nitride______Mg3N2

b. Iron (III) chloride __FeCl3______

c. __ Dinitrogen oxide or (monoxide) N2O

d. ammonium sulfate __(NH4)2SO4__

10. (4pts) Which compound(s) above are ionic? Mg3N2, (NH4)2SO4, FeCl3

11. (3pts) Circle the statement below which best describes an isotope (you may circle more than one answer).

a. Two atoms that have the same atomic number but differ in the mass number b. Two atoms that are in the same period on the periodic chart. c. Two atoms that are in the same row on the periodic chart. d. Two atoms that differ only in the number of neutrons in the nucleus. e. An atom that has an unequal amount of protons and electrons f. An atom that has a full shell of valence electrons.

12. (3pts) The ability of an atom to attract the shared electrons in a covalent bond is its

a. bonding ability b. electronegativity c. polarity d. ionic character e. nonpolarity

13. (3pts) In a molecule with covalent bonding,

a. oppositely charged ions are held together by strong electrical attractions. b. atoms of metals form bonds to atoms of nonmetals. c. atoms of different metals form bond. d. atoms are held together by sharing electrons. e. atoms of noble gases are held together by attractions between oppositely charged ions.

14. (3pts) The element in this list with chemical properties similar to magnesium is

a. sodium b. boron c. carbon d. strontium e. chlorine (elements within a group have similar chemical properties…Group 1 alkali metals, Group 2 alkaline earth metals, Group 7 halogens, Group 8 noble gases) 15. (3pts) Which of the following numbers contains the designated CORRECT number of significant figures? a. 0.04300 5 sig figs (4sig figs) b. 0.00302 2 sig figs (3 sig figs) c. 156,000 3 sig figs d. 1.04 2 sig figs (3 sig figs) e 3.0650 4 sig figs (5 sig figs)

16. (3pts) The correct answer for the addition of 7.5g + 2.26g + 1.311g + 2g is

a. 13.071g b. 13g c. 13.0g d. 10g e. 13.1g

We are doing addition, so we need to look at the digit places. 2g only goes out to the ones place, so our answer will be to the nearest ones.