CR Chapter 7: Numbers in Chemistry

Convert 32,000. into scientific notation.

• 32.000 x 10³

• 3.2000 x 10⁴

• 32000 x 10²

• 0.32000 x 10^-2

Answer explanation

To convert 32,000. into scientific notation, move the decimal point to the left until there is only one non-zero digit to the left. The number of times the decimal was moved is the exponent and it is positive because 32,000. is a large quantity. The correct choice is 3.2000 x 10⁴.

Convert 6.02x10² to standard notation

• 6.02

• 60.2

• 602

• 0.602

Answer explanation

To convert 6.02x10² to standard notation, move the decimal point two places to the right to make the number represent a large quantity. The correct choice is 602.

How many Sig Figs are in 0.00025?

• 1

• 2

• 3

• 4

Answer explanation

There are 2 significant figures in 0.00025 because all non-zero digits and zeros between them are significant. Leading zeros are not counted as a significant figure.

Round 5.235874 to 3 Sig Figs

• 5.23

• 5.235

• 5.236

• 5.24

Answer explanation

To round 5.235874 to 3 significant figures, we look at the digit after the third significant figure. Since it is 8, we round up the last significant figure. Therefore, the correct answer is 5.24.

How many Sig Figs are in 25.00?

• 1

• 2

• 3

• 4

Answer explanation

There are 4 significant figures in 25.00 because all the non-zero digits are significant and zeros at the end with a decimal point are also significant.

This bullseye demonstrates...

• High Accuracy & High Precision

• High Accuracy & Low Precision

• Low Accuracy & High Precision

• Low Accuracy & Low Precision

Answer explanation

This bullseye demonstrates low accuracy and high precision, as it consistently hits the same spot but not the target center.

What conversion factor would be best for this problem?

• 1 kg / 2.2 lbs

• 2.2 lb / 1 kg

• 1000 g / 1 kg

• 1 kg / 1000 g

Answer explanation

The best conversion factor for this problem is 2.2 lb / 1 kg because it correctly places kg in the denominator to cancel it and places lb in the numerator to convert to it.

Calculate the following to the correct number of sig figs.
0.00401  x  2.00  x  501

• 4.02

• 4

• 4.0

• 4.0180

Answer explanation

To calculate the product of 0.00401, 2.00, and 501 to the correct number of significant figures, multiply them together. The correct answer is 4.02, which has the same number of significant figures as the number with the fewest significant figures in the original numbers.

Calculate the following to the correct number of sig figs.

32.451 - 21.5

• 11.0

• 10.951

• 11

• 10.95

Answer explanation

To subtract numbers with different decimal places, align the decimal points and subtract. The correct answer is 11.0 because it has the same number of decimal places as the least precise number being subtracted.

Calculate the following to the correct number of sig figs.

13.2017 / 17.10

• 0.772

• 0.7720

• 0.772030

• 0.77

Answer explanation

To calculate the division to the correct number of sig figs, we need to consider the number with the least sig figs. In this case, 17.10 has 4 sig figs. Therefore, the answer should have 4 sig figs as well. The correct choice is 0.7720, which has 4 sig figs.