+1 (218) 451-4151 info@writersnest.org

Carry out the following calculations and express answers to correct numbers of
significant figures:
A.  (97.54)(3.1457)                                     B.  8.625-7.1 C.( 13.723)(0.504) – .21
D.6.023×1023                                       E. (1.234)(5.321)
8.314×108                                          2.69
2. Considering an atom of atomic number 48.
A. what is its number of protons?
B. What is its number of electrons?
C. If the mass number is 112, how many neutrons are there?
D. Name the element.
E. How does the atom become an ion with a
charge of +2?
3  A step in determining Lewis formulas of covalent species is to find the total
number of electrons that are used in the formula. Find such totals for the
A. OF2                   B. CO32-                          C.  HBr                     D.  NCl3                            E. H2S
Note: This question says to give just the numbers of electrons. It does not
require  writing of the Lewis formulas.
4.     An atom of Mg has a mass of 24.31 (atomic mass units).
An atomic mass units is 1.6605×10-24 grams. What is the mass of the mg atom in:
A. grams                                     B. kilograms.
5.Two samples containing C and H are analyzed. Sample 1 has 6.00g of C and
2.02g of H.   Sample 2 has 12.01gC and 3.02g H. Giving reasons for your answer,
are the two samples the same or different compounds