Exam 1Chem 1AName______
Dr. SommaSeptember, 10 2008100 points
Watch units and significant figures.Show all work to receive full credit.Return the card after completing the exam.
1. (15 pts.)Multiple choice.Circle the correct answer.
(i)Which of the following processes is a chemical change:
a.Ice cream melting.
b.Wood burning.
c.Steam developing from a boiling pot of water.
d.None of the above.
(ii)Density is:
a.An intensive property.
b.Only liquids have this property.
c.A state of matter.
d.An extensive property.
(iii)What does the atomic number represent?
a.Number of electrons in the nucleus.
b.Number of neutrons and protons in the nucleus.
c.Number of isotopes for an element.
d.Number of protons in the nucleus.
(iv)What are rays?
a.Positively charged particles.
b.Same as X rays.
c.Electrons.
d.Neutrons.
(v)What elements of the periodic table can form more than one type of cation?
a.Alkali metals.
b.Noble gases.
c.Transition metals.
d.Halogens.
2. (6 pts.)Express, where appropriate, the answer to the following in scientific notation, using the correct number of significant figures:
a.(213.3642 + 17.54+ 32978) = ______
b.(9.11 x 10-31) x (2.997925 x 108) = ______
3. (12 pts.)Fill in the blanks:
SymbolAtomic number# of NeutronsMass number
______
a.______22______48
b.______110184
c.______60
4. (16 pts.)Fill in the blanks by providing either the chemical formula or the name of the compound.
Chemical FormulaName of the Compound
NaHCO3______
PbCr2O7______
Be(ClO)2______
Cr2(SO4)3______
______carbon tetrachloride
______silver permanganate
______mercury (II) thiocyanate
______ammonium nitrate
5. (8pts.)An average man requires about 2.00 mg of riboflavin (vitamin B12) per day. How many pounds of cheese would a man have to eat per day if this were his only source of riboflavin and if the cheese contained 5.5 g of riboflavin per gram? (1 pound = 453.6 g).
6. (4 pts.)Convert 300oC Celsius in the Fahrenheit scale.
uniformely
7. (6 pts.)The normal lead (Pb) content in human blood is about 0.40 part per million (ppm) (0.40 g of Pb per million grams of blood). A value of 0.80 ppm is considered to be dangerous. How many grams of lead are contained in 6.0 x 103 g of blood (the amount in an average adult) if the Pb content is 0.62 ppm?
8. (12 pts.)a. To identify a liquid substance, a student determined its density. Using a graduate cylinder, she measured out a 45 mL sample of the substance. She then measured the mass of the sample, finding that it weighted 38.5 g. She knew that the substance had to be either isopropyl alcohol (density = 0.785 g/mL) or toluene (density = 0.866g/mL). What are the calculated density and the probable identity of the substance?
b. An experiment requires 45.0 g of ethylene glycol (density = 1.114 g/mL). Rather then weight the sample on the balance, a chemist chooses to dispense the liquid using a graduate cylinder. What volume of the liquid should he use?
9. (9 pts.)Naturally occurring boron consists of 80.22% 11B (atomic mass = 11.009 amu) and 19.78% of another isotope. To account for a total atomic mass of 10.810 amu from both isotopes, what must be the atomic mass of the second isotope?
10. (12 pts.)Consider the work done by Rutherford to probe the positive charge distribution of the atom.
a. What did Rutherford observe when he measured the scattering of the particles by apiece of gold foil?
b. How did Rutherford’s results contradict the “plum pudding” model proposed by Thomson in which electrons were believed to be embedded in a uniform, positively charged sphere?