Answer: " 0.69 g / mL "
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Explanation:
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The "pre-lab question" given is:
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"The volume of an unknown liquid is 15 ml, and the mass of the liquid and the graduated cylinder it is in is 55.2g. If the mass of the graduated cylinder is 44.8g , what is the density of the unknown liquid? " .
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Note: The volume of the unknown liquid is 15 mL ; regardless of whether or not the "unknown liquid" is in the graduated cylinder.
The density of the unknown liquid is measured in: "g / mL " ;
that is, "grams per mL" .
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Note: "D = m / V " ; that is; "Density = mass/ volume" ;
that is: ["Density = mass per 'unit volume' ]" .
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So; to find the density, "D" , of the "unknown liquid" ; we would have to find the "mass" of the "unknown liquid" by "subtracting" :
the "known mass of liquid when the liquid is not in the cylinder"; that is: " 44.8g" ; From:
the "known combined value of the: 'mass of the liquid PLUS the mass of the cylinder" ; that is: "55.2g" ;
→ " 55.2g - 44.8g = 10.4g " .
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So: " D = m / V " ; (55.2g - 44.8 g) / 15 mL " ;
= (55.2g - 44.8 g) / 15 mL " ;
= (10.4g) / 15mL ;
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Note that the "Density" = mass per "unit volume" ;
→ So: D = m / V ; in units of: " g / mL " (grams per millileter) ;
= (10.4g) / 15mL ;
= [ (10.4) / 15 } g/ mL ;
= 0.693333333333333.... g / mL ;
→ We round to "2 (two) significant figures" ;
→ since we have: "10.4 g / 15 mL " ;
and 15 mL is considered a measured/experimental value;
and: 10.4g is considered a measured/experimental value;
→ so, the least precise value; 15 mL (has only 2 (two) significant figures ;
compared to other value: 10.4g (which has 3 (three) significant figures;
→ so we shall round off to 2 (two) significant figures:
= 0.69 g / mL
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→ which is our answer: " 0.69 g / mL " .
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