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Question 3 (10 points)

Which statements are true in the following choice? Select all that apply.

Question 3 options:

A.	Lecture Notes topic: "Percent Composition Textbook section: 3.8". The percent by weight composition shows the density of a component inside 100 g of a whole item. Its expression is as follows: % by weight = (weight of component x weight of whole set) / 100
B.	Lecture Notes topic: "Percent Composition Textbook section: 3.8". The percent by weight composition shows the proportion of a component inside 100 g of a whole item. Its expression is as follows: % by weight = (weight of component / weight of whole set) x 100
C.	The expression of the percent composition can be rearranged to to get: weight of component = % by weight / weight of whole set x 100
D.	The expression of the percent composition can be rearranged to to get: weight of component = % by weight x weight of whole set / 100
E.	The expression of the percent composition can also be rearranged to to get: weight of whole set = weight of component / % by weight x 100
F.	The expression of the percent composition can also be rearranged to to get: weight of whole set = weight of component x % by weight / 100

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Question 4 (10 points)

Which statements are true in the following choice? Select all that apply.

Question 4 options:

A.	Lecture Notes topic: "Percent Composition Textbook section: 3.8" and "Illustration (Continued)" If the weight of a compound is not known but its formula is known, figuring out the % composition of the components of the compound can be done using the atomic number obtained using the formula of the compound and its components and the periodic table.
B.	Lecture Notes topic: "Percent Composition Textbook section: 3.8" and "Illustration (Continued)" If the weight of a compound is not known but its formula is known, figuring out the % composition of the components of the compound can be done using the molar weight, obtained using the formula of the compound and its components and the periodic table.
C.	For example, the % composition of Ca in Ca3(PO4)2 is 100 x (3 x 40.01) / (3 x 40.01+ 2 x 30.97+ 8 x 16.0) = 38.72%
D.	For example, the % composition of Ca in Ca3(PO4)2 is 100 / (3 x 40.01)x (3 x 40.01+ 2 x 30.97+ 8 x 16.0) = 35.8 %

Answer 1

Question 3: we have ,

%weight of component = weight of component × 100 / total weight of all the components.

Weight of component=(%weight of component × total weight of all the components) /100

total weight of all the components = (weight of component × 100) / %weight of component

based upon the above expressions only B and D are correct.

Question 4;

we can find the percentage composition from the molecular formula also based upon the atomic weights. for example for a compound A_xB_y, the %weight of A= x (atomic mass of A) (100) / [x (atomic mass of A)+ y( atomic mass of B).

hence statement A is wrong because it talks about atomic number not mass.

thus B is true statement, C is also true as the formula used is right while as D is false statement.