Q: If you have 2.40 x $$10^{-4}$$ moles of a substance, how many particles do you have? (Use Avogadro's number: $$6.022 \times 10$$^{23}$$ particles/mole)

$$1.45 \times 10$$^{20}$$ particles

Q: A sample contains $$4.78 \times 10$$^{20}$$ molecules. How many moles does this represent? (Use Avogadro's number: 6.022$$ \times $$10^{23}$$ molecules/mole)

$$7.94 \times 10$$^{-4}$$ moles

Question 1

Which of the following is the correct value and scientific notation for Avogadro's number?

Accepted Answer

$$6.022 	imes 10$$^{23}$$

Question 2

Which SI unit is correctly matched with its physical quantity?

Accepted Answer

Meter = length

Question 3

A student records a measurement as 0.00450 g. How many significant figures does this value have?

Accepted Answer

3

Question 4

Which of the following numbers contains exactly 4 significant figures?

Accepted Answer

2.340

Question 5

If you have 2.40 x $$10^{-4}$$ moles of a substance, how many particles do you have? (Use Avogadro's number: $$6.022 	imes 10$$^{23}$$ particles/mole)

Accepted Answer

$$1.45 	imes 10$$^{20}$$ particles

Question 6

Which prefix and its value is correctly matched?

Accepted Answer

milli = 0.001

Question 7

Which of the following statements about significant figures is TRUE?

Accepted Answer

Non-zero numbers are always significant.

Question 8

A laboratory measurement is recorded as 0.000240 L. How many significant figures are in this measurement?

Accepted Answer

3

Question 9

Which of the following best explains why prefixes like 'kilo-' and 'milli-' are used in the SI system?

Accepted Answer

To make measuring easier by expressing very large or small quantities in manageable numbers.

Question 10

Which of the following numbers has 5 significant figures?

Accepted Answer

0.004500

Question 11

A sample contains $$4.78 	imes 10$$^{20}$$ molecules. How many moles does this represent? (Use Avogadro's number: 6.022$$ 	imes $$10^{23}$$ molecules/mole)

Accepted Answer

$$7.94 	imes 10$$^{-4}$$ moles

Question 12

Which of the following is NOT an SI base unit?

Accepted Answer

Celsius

Question 13

Which of the following best describes when zeros are significant in a measured value?

Accepted Answer

Zeros are significant only if they are between non-zero digits or after a decimal point and a non-zero digit.

Question 14

Convert 0.0024 kilometers to meters using SI prefixes.

Accepted Answer

Question 15

A beaker contains 1.42 L of water. How many significant figures are in this measurement?

Accepted Answer

3

Question 16

Which of the following is the correct conversion for 1 milliliter (mL) in liters (L)?

Accepted Answer

$$1 	imes 10$$^{-3}$$ L

Question 17

A scientist measures a sample as 0.000780 g. Which statement about the significant figures in this measurement is correct?

Accepted Answer

There are 3 significant figures.

Question 18

Which of the following best describes the purpose of using scientific notation in chemistry?

Accepted Answer

To express very large or very small numbers in a more manageable form.

Fundamental Concepts: SI Units, Prefixes, and Significant Figures in Chemistry

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