Question
A student recorded the volume of a gas as \({\text{0.01450 d}}{{\text{m}}^{\text{3}}}\). How many significant figures are there in this value?
A. 3
B. 4
C. 5
D. 6
▶️Answer/Explanation
B
The first two zeroes in 0.01450 are insignificant because they are before the first non-zero digit, and the last zero is significant because it is after the first non-zero digit.
Hence, it has 4 significant figures.
Question
Which would be the best method to decrease the random uncertainty of a measurement in an acid-base titration?
A. Repeat the titration
B. Ensure your eye is at the same height as the meniscus when reading from the burette
C. Use a different burette
D. Use a different indicator for the titration
▶️Answer/Explanation
A
Random error or random uncertainty occurs due to chance. There is always some variability when a measurement is made. Random error may be caused by slight fluctuations in an instrument, the environment, or the way a measurement is read, that do not cause the same error every time. In order to address random error, scientists utilized replication. Replication is repeating a measurement many times and taking the average. Hence, repeating the titration would be the best method to decrease the random uncertainty of a measurement in an acid-base titration.
Question
Which are likely to be reduced when an experiment is repeated a number of times?
A. Random errors
B. Systematic errors
C. Both random and systematic errors
D. Neither random nor systematic errors
▶️Answer/Explanation
A
Random error occurs due to chance. There is always some variability when a measurement is made. Random error may be caused by slight fluctuations in an instrument, the environment, or the way a measurement is read, that do not cause the same error every time. In order to address random error, scientists utilized replication. Replication is repeating a measurement many times and taking the average.
Question
How many significant figures are there in 0.00370?
A. 2
B. 3
C. 5
D. 6
▶️Answer/Explanation
B
The first three zeroes in 0.00370 are insignificant because they are before the first non-zero digit, and the last zero is significant because it is after the first non-zero digit.
Hence, 0.00370 has 3 significant figures.
Question
Density can be calculated by dividing mass by volume. \(0.20 \pm 0.02{\text{ g}}\) of a metal has a volume of \(0.050 \pm 0.005{\text{ c}}{{\text{m}}^{\text{3}}}\). How should its density be recorded using this data?
A. \(4.0 \pm 0.025{\text{ g}}\,{\text{c}}{{\text{m}}^{ – 3}}\)
B. \(4.0 \pm 0.8{\text{ g}}\,{\text{c}}{{\text{m}}^{ – 3}}\)
C. \(4.00 \pm 0.025{\text{ g}}\,{\text{c}}{{\text{m}}^{ – 3}}\)
D. \(4.00 \pm 0.8{\text{ g}}\,{\text{c}}{{\text{m}}^{ – 3}}\)
▶️Answer/Explanation
B
g
\(d=\frac{M}{V} = \frac{0.2}{0.050}\) = 4.0 g/. (d should be taken upto maximum of M and V, (i.e. maximum of 1 and 2 ) = 2 significant digits).
\(\frac{\Delta d}{d}=\pm (\frac{\Delta M}{M} + \frac{\Delta V}{V})\)
\(\frac{\Delta d}{4}=\pm (\frac{0.02}{0.2} + \frac{0.005}{0.050})\)
\(\Delta d\) = \(\pm0.8\)
g/.