Question

D. MORE PRACTICE... 1. Complete the table below. Massm m # moles Substance Mass (g) Molar mass (g/mol) of moles a. Aspirin tablet C.H.O.) 0.325 b. Wooden stick | (CHO) 14.482 c. Copper wire (Cu) Show work below. 1.809 2. A substance has a mass of 90.10 grams and contains 3.02 x 10 molecules. Which of the 3 substances in the chart above is it? Explain. 0 2 3 Fird noo or mores find mm mass per ind look at the Chaft/ find the sub with closter

Answer 1

Quesstion 1)

a) As the molecular formula of aspirin is, C9H8O4, the molecular mass can be calculated using following formula,

molar mass = (atomic mass of C x number of carbon) + (atomic mass of H x number of H) + (atomic mass of O x number of O)

The atomic masses of C, H and O are 12, 1 and 16, respectively.

Therefore,

molar mass of C9H8O4 = (12 x 9) + (1 x 8) + (16 x 4) = 180 g/mol

Therefore, molar mass of C9H8O4 is 180 g/mol.

The number of moles of C9H8O4 can be calculated using following formula,

Number of moles of C9H8O4 = Wieght of C9H8O4 in g / molar mass of C9H8O4 in g/mol

= 0.325 / 180 = 0.0018 moles

The number of moles of C9H8O4 is 0.0018 moles

b) The molar mass of CH2O = (12 x1) + (1 x 2) + ( 16 x1) = 30 g/mol

The number of moles of CH2O = Weight of CH2O in g / molecular weight in g/mol

= 14.482 g / 30 g/mol

= 0.483 moles

Therefore, number of moles of CH2O is 0.483 moles.

c) molar mass of Cu is = atomic mass of Cu = 63.54 g/mol

number of moles of Cu = Weight of Cu in g / molecular weight of Cu in g/mol

= 1.809 g/ 63.54 g/mol

= 0.0284 moles

Therefore, number of moles of Cu is 0.0284 moles

Question 2)

Let us first find the number of moles of substance.

As,

Number of molecules = number of moles x Avagadro's number (6.022 x 10²³)

Here, number of molecules = 3.02 x 10^23.

rearranging the above equation for number of moles of substance, we get

number of moles = number of molecules / avagadro,s number

= (3.02 x 10²³) / 6.022 10²³

= 0.5 moles

Now, the molecular weight of the substance can be calculated using following formula,

Molecular weight = Weight in g / number of moles

= 90.10 g / 0.5 = 180.2 g/mol = 180 g/mol

Therefore, the substance is Aspirin.