This is true i think if that is a question
The answer is 25 grams for this question
Answer:
Aluminium was named after alum, which is called 'alumen' in Latin. This name was given by Humphry Davy, an English chemist, who, in 1808, discovered that aluminium could be produced by electrolytic reduction from alumina (aluminium oxide), but did not manage to prove the theory in practice.
Explanation:
Answer:
The molar mass of the unknown non-electrolyte is 64.3 g/mol
Explanation:
Step 1: Data given
Mass of an unknown non-electrolyte = 2.17 grams
Mass of chloroform = 225.0 grams
The freezing point of the resulting solution is –64.2 °C
The freezing point of pure chloroform is – 63.5°C
kf = 4.68°C/m
Step 2: Calculate molality
ΔT = i*kf*m
⇒ ΔT = The freezing point depression = T (pure solvent) − T(solution) = -63.5°C + 64.2 °C = 0.7 °C
⇒i = the van't Hoff factor = non-electrolyte = 1
⇒ kf = the freezing point depression constant = 4.68 °C/m
⇒ m = molality = moles unknown non-electrolyte / mass chloroform
0.7 °C = 1 * 4.68 °C/m * m
m = 0.150 molal
Step 3: Calculate moles unknown non-electrolyte
molality = moles unknown non-electrolyte / mass chloroform
Moles unknown non-electrolyte = 0.150 molal * 0.225 kg
Moles unknown non-electrolyte = 0.03375 moles
Step 4: Calculate molecular mass unknown non-electrolyte
Molar mass = mass / moles
Molar mass = 2.17 grams / 0.03375 moles
Molar mass = 64.3 g/mol
The molar mass of the unknown non-electrolyte is 64.3 g/mol
The question is missing the data sets.
This is the complete question:
A single penny has a mass of 2.5 g. Abbie and James
each measure the mass of a penny multiple times. Which statement about
these data sets is true?
O Abbie's measurements are both more accurate
and more precise than James'.
O Abbie's measurements are more accurate,
but less precise, than James'.
O Abbie's measurements are more precise,
but less accurate, than James'.
O Abbie’s measurements are both less
accurate and less precise than James'.
Penny masses (g)
Abbie’s data
2.5, 2.4, 2.3, 2.4, 2.5, 2.6, 2.6
James’ data
2.4, 3.0, 3.3, 2.2, 2.9, 3.8, 2.9
Answer: first option, Abbie's measurements are both more accurate
and more precise than James'.
Explanation:
1) To answer this question, you first must understand the difference between precision and accuracy.
<span>Accuracy is how close the data are to the true or accepted value.
</span>
<span>Precision is how close are the data among them, this is the reproducibility of the values.</span>
Then, you can measure the accuracy by comparing the means (averages) with the actual mass of a penny 2.5 g.
And you measure the precision by comparing a measure of spread, as it can be the standard deviation.
2) These are the calculations:
Abbie’s data
Average: ∑ of the values / number of values
Average = [2.5 + 2.4 + 2.3 + 2.4 + 2.5 + 2.6 + 2.6 ] / 7 = 2.47 ≈ 2.5
Standard deviation: √ [ ∑ (x - mean)² / (n - 1) ] = 0.11
James’ data
Average = [2.4 + 3.0 + 3.3 + 2.2 + 2.9 + 3.8 + 2.9] / 7 = 2.56 ≈ 2.6
Standard deviation = 0.53
3) Conclusions:
1) The average of Abbie's data are closer to the accepted value 2.5g, so they are more accurate.
2) The standard deviation of Abbie's data is smaller than that of Jame's data, so the Abbie's data are more precise.
