# Chemistry Concept Problems

1. (a) Express 50 days in seconds (b) Convert 3.75 meter/sec

to km/hr. Express the results in scientific notation.

2. Perform the following operations and express the answer

with the appropriate number of significant figures.

863[1255-(3.45*10.8)]

3. The recommended dose of Elexophyllin (a drug used to treat

asthma) is 6 mg/kg of body mass. Calculate the dose in milligrams (mg)

required for a 150lb person?

4. Determine the number of protons, neutrons, and electrons

present in (a) an atom of 138Ba (b) 81Br1- (note that the Br atom gains

1 electron to become negatively charged and becomes an anion (Br1-)

5. Magnesium has (3) isotopes with mass numbers 24, 25 and 26

(a) write the chemical symbol of each using the established convention

discussed in class. (b) How many neutrons are present in the nuclide of

each isotope?

6. Write the electron configuration for: (a) H, Li, Na, and K

(b) Be, Mg, and Ca (c) Fe, Ni, and Zn

7. The Chemical formula HNO3 (nitric acid) as written

indicates 1 molecule of HNO3 contains_____________atom(s) of N

and___________ atom(s) of O and a total of_____________atom(s). This

compound is called a ________________compound.

8. The formula weight (molecular weight) of nitric acid

is_____________amus.

9. In the formation of sodium chloride (table salt), the

sodium atom loses an electron and becomes______________charged. The

sodium ion formed is called a_______________. In the process the

chlorine atom gains an electron to become an____________.

10. The mercury concentration in a polluted lake is 0.0125*10 neg 6 mg/L, what is the total mass in kilograms of mercury in the lake is approximately circular with a diameter (d) of 10 miles and average depth (h) of 50 ft? Note that the volume is calculated as follows: V=3.142*(d/2)2*h.

Useful conversion factors: 1000 g=1kg; 1000 mg=1 g

5280 feet=1 mile; 28.317 (L) liters=1 cubic feet

#### Solution Preview

1.(a) Express 50 days in seconds (b) Convert 3.75 meter/sec to km/hr. Express the results in scientific notation.

a.50 Days = 50

x 24 hrs = 1200 hrs

x ...

#### Solution Summary

This solution provides an excellent source of practice of chemistry concepts. It helps you solve few basic but important questions from chemistry making your concepts strong.