Q: What is the correct formula for calculating the percentage of a component in a mixture?

$$\text{Percentage} = \dfrac{\text{Component}}{\text{Total}} \times 100$$

Q: A student measures the mass of lead in a sample to be 11.6 g out of a total mass of 11.74 g. What is the percentage of lead in the sample?

$$\dfrac{11.6}{11.74} \times 100 = 98.8\%$$

Question 1

Which statement best describes the difference between substances with the same chemical composition but different functions, such as various brands of toothpaste?

Accepted Answer

They have the same chemical composition and properties, but their functions differ due to added ingredients or formulation.

Question 2

What is the correct formula for calculating the percentage of a component in a mixture?

Accepted Answer

$$	ext{Percentage} = \dfrac{	ext{Component}}{	ext{Total}} 	imes 100$$

Question 3

A student measures the mass of lead in a sample to be 11.6 g out of a total mass of 11.74 g. What is the percentage of lead in the sample?

Accepted Answer

$$\dfrac{11.6}{11.74} 	imes 100 = 98.8\%$$

Question 4

Which of the following is the correct scientific notation for the number 0.00000726?

Accepted Answer

$$7.26 	imes 10$$^{-6}$$

Question 5

In the context of electromagnetic radiation, what is the relationship between wavelength and energy?

Accepted Answer

Shorter wavelength corresponds to higher energy.

Question 6

Which experiment led to the discovery of the electron and disproved the 'plum pudding' model of the atom?

Accepted Answer

J.J. Thomson's cathode ray experiment

Question 7

What is the atomic number of an element, and what does it represent?

Accepted Answer

The number of protons; it defines the identity of the element.

Question 8

An atom has 17 protons and 18 electrons. What is the charge of this atom?

Accepted Answer

Negative (-1)

Question 9

Which of the following statements about metals is TRUE?

Accepted Answer

Metals are shiny, ductile, and good conductors of heat.

Question 10

Which group in the periodic table contains the noble gases?

Accepted Answer

Group 8A

Question 11

What is the correct order of filling electron sublevels according to the Aufbau principle?

Accepted Answer

$$1s \rightarrow 2s \rightarrow 2p \rightarrow 3s \rightarrow 3p \rightarrow 4s \rightarrow 3d$$

Question 12

Which of the following is NOT a characteristic of nonmetals?

Accepted Answer

Good conductor of heat

Question 13

If an atom has a mass number of 23 and an atomic number of 11, how many neutrons does it have?

Accepted Answer

12

Question 14

Which of the following best describes the periodic table arrangement?

Accepted Answer

Elements are arranged in order of increasing atomic number.

Question 15

A cation is formed when:

Accepted Answer

An atom loses electrons.

Question 16

Which of the following is a correct example of scientific notation for a very small number?

Accepted Answer

$$7.50 	imes 10$$^{-7}$$

Question 17

Which of the following statements about isotopes is TRUE?

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons.

Question 18

Which of the following is a property of metalloids?

Accepted Answer

They have properties intermediate between metals and nonmetals.

Question 19

Which of the following best explains why electrons are not included in the atomic mass of an atom?

Accepted Answer

Electrons have a negligible mass compared to protons and neutrons.

General Chemistry 1: Foundations, Atomic Structure, and the Periodic Table

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