346.37 g/mol O 452.73 g/mol Question 15 2 points The molar mass of aluminum is 2

Question

346.37 g/mol O 452.73 g/mol Question 15 2 points The molar mass of aluminum is 26.982 g/mol. Convert 0.0275 mol of aluminum to grams. Report your answer to three significant figu answer is a decimal, include a zero to the left of the decimal point (ex. 0.234 g not 234 g) Question 16 3 points How many grams of magnesium would contain the same number of atoms as 131.29 g of xenon? Report your answer to three signitc 3 points Question 17 Match each element with the number of moles contained within 1.00 gram of that element A. 0.00762 mol 8. 0.00890 mol C. 0.0411 mo - magnesium cadmium #!xenon - 3 poi Question 18 r mass is 132 A compound comprisinq carbon, hydrogen, and oxygen has the empirical formula C2Ha0 If the pokworm-infected-ch....Jpg 2 7

Explanation / Answer

Significant figures rules

Perform operations as usual... then

account for the significant figures of each number.

Recall:

- ZEROS to the left do NOT matter ; 0.02 and 0.2 will have 1 sig. fig (digit = 2)

- ZEROS between numbers, DO matter 0.0202 and 0.202  will have 3 sig fig (digits 2, 0 and 2)

- ZEROS to the right, DO matter, since those show precise data i.e. 2.0 vs. 2.00 exists (2 sig fig. vs 3 sig. fig)

Then... apply rule, round as required

* Addition / Subscraction --> round answer to the LEAST sig. fig of the operation ( i.e. 2 sig fig vs. 3 sig fig --> round to 2 sig. fig)

* Multiplication/Division --> round answer to the LEAST sig. fig of the operation ( i.e. 2 sig fig vs. 3 sig fig --> round to 2 sig. fig)

Q15

3 sig fig ...

26.982 --> 27.0

Q16

mass of Mg from

131.29 g of xenon

mol of xe = mass/MW = 131.29/131.29 = 1 mol

then

6.022*10^23 atoms

therefore,

1 mol of Mg as well

1 mol of Mg = 24.30500 --> use only 5 sig fig, since Xe = 5 fig sig --> 24.305 g/mol

Q17

1 gram of element:

MW of Mg < MW of Cd < Mw of Xe

then

mol of MG > mol of Cd > mol of Xe

that is

0.0411 Mg > 0.00762 Cd > 0.00290 Xe

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