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# 1. Calculate (to the nearest 0.1 u) the formula mass of these

### Customer Question

1. Calculate (to the nearest 0.1 u) the formula mass of these compounds.
(a) aluminum peroxide, Al2(O2)3 ________u 2*(mass of Al)+6*(mass of O)...do this for all of these
(b) rubidium nitrate, RbNO3___________u
(c) carbon dioxide, CO2__________u

2. Find the percentage by mass of Cl in MgCl2 if it is 25.1% Mg by mass. _____%
If it is 25.1 % by mass Mg, then it is 100-25.1% Cl by mass because there is only Mg and Cl in this compound
3.

Determine the percentage by mass of each element in the following compounds.
(a) salt, NaCl do this:
Na_________% (mass of Na)/(mass of NaCl)
Cl_________% (mass of Cl)/(mass of NaCl)

(b) grain alcohol, C2H5OH
C_______% do the same thing as above
H_______%
O_______%

4. In a lab experiment, 7.35 g of phosphorus reacts with bromine to form 64.19 g of phosphorus tribromide.
(a) Calculate the percentage by mass of P in phosphorus tribromide._______% (mass of P)/(mass of phosphorus tribromide) mass of phosporous tribromide=mass of phosporous+3*mass of bromine
(b) How many grams of bromine reacted?_______g There are only two elements present: phosphorus and bromine. In the end we have 64.19 g of PBr3 and 7.35 g of that is P, so the rest is bromine. So the grams of bromine is 64.19g -7.35g
How do you know? ________
law of constant composition, law of conservation of mass, law of multiple proportions, or law of definite proportions?

5. In a lab experiment, 7.75 g of phosphorus reacts with bromine to form 67.68 g of phosphorus tribromide. How much phosphorus tribromide would be formed if 10.00 g of phosphorus reacted with 61.10 g of bromine?_______g
How do you know?
law of constant composition Dalton's law law of definite proportions law of conservation of mass ?

6. Referring only to a periodic table, give the ionic charge expected for each of these representative elements. Look at the periodic table we labeled. Find the element, and then look at the column that the element is in, and it will have the charge there.
(a) B

(b) Cl

(c) Rb

(d) Al

(e) O

(f) C

(g) Kr

(h) P

Referring only to a periodic table, give the number of covalent bonds expected for each of these representative elements. This is the same as the problem above. Number of bonds=the charge. So if you find the element and its column is labeled +4/-4, it will make 4 bonds, -3=3 bonds, etc.
(a) S

(b) Kr

(c) Ne

(d) Ge

(e) C
Submitted: 6 years ago.
Category: Homework
Expert:  akch2002 replied 6 years ago.
Do you still require answers for these problems?
Customer: replied 6 years ago.
no thanks the answers were needed sooner
Expert:  akch2002 replied 6 years ago.
No problem.