Answer:
8700
Explanation:
First, do the operations i<em>nside parentheses</em>.
102 900/12 = 8600 2 sfs because of 12
170/1.27 = 130 2 sfs because of trailing 0 in 170
===============
Now, do the addition.
8600
<u> + </u><u>13</u><u>0
</u>
8700
The answer has two significant figures because when adding, you must round your answer to the same "place" as the measurement with its last significant figure furthest to the left.
The last significant figure in 8600 (the 6, in the hundreds place) is further to the left than the last significant figure in 130 (the 3, in the tens place).
We round off to the nearest hundred and get the answer, 8700.
Answer: The sample that contains the greater number of molecules is water.
Explanation: To calculate the number of molecules, it is used the Avogadro's number ( 
particles/molecules). So, considering that the mass to water and carbon dioxide is 1g (it can be any other number), the relationship between moles and molar weight is:
To water: 
= 0.05 moles.
Therefore,
1 mol ---- molecules
0.05 moles ---- x
x = 
molecules of water.
To carbon dioxide: 
= 0.02 moles.
Therefore,
1 mol ---- molecules
0.02 moles ---- y
y = 
molecules of carbon dioxide.
