Q: How many atoms are present in $$75.0$$ grams of mercury ($$Hg$$)? (Atomic mass of $$Hg = 200.59 g/$$mol, Avogadro’s number $$= 6.02 \times 10$$^{23}$$ atoms/mol)

$$2.25 \times 10$$^{23}$$ atoms

Question 1

Which scientist is credited with providing the first convincing evidence for the atomic theory, explaining the laws of conservation of mass, definite proportions, and multiple proportions?

Accepted Answer

John Dalton

Question 2

According to the law of definite proportions, which of the following statements is correct?

Accepted Answer

All samples of a given compound have the same proportions of their constituent elements.

Question 3

Which experiment led to the discovery of the electron and the measurement of its charge-to-mass ratio?

Accepted Answer

Thomson's cathode ray tube experiment

Question 4

A neutral atom of sodium (Na) has an atomic number of 11. How many electrons does it have?

Accepted Answer

11

Question 5

Which of the following statements best describes the difference between isotopes of the same element?

Accepted Answer

They have different numbers of neutrons.

Question 6

Calculate the average atomic mass of silicon given the following data:
Silicon-28: $$27.9769$$ amu, $$92.28\%$$ abundance
Silicon-29: $$28.9765$$ amu, $$4.70\%$$ abundance
Silicon-30: $$29.9738$$ amu, $$3.02\%$$ abundance

Accepted Answer

$$28.09$$ amu

Question 7

Which group of elements is known for being mostly unreactive and is commonly used in lighting and balloons?

Accepted Answer

Noble gases

Question 8

A sample of water is decomposed into $$16.0$$ grams of oxygen and $$2.0$$ grams of hydrogen. What is the mass ratio of oxygen to hydrogen in water?

Accepted Answer

$$8:1$$

Question 9

Which of the following statements about metals is FALSE?

Accepted Answer

Metals tend to gain electrons during chemical changes.

Question 10

A certain element has two naturally occurring isotopes: $$X-10 ($$mass $$10.0129$$ amu, $$19.91\%$$ abundance) and $$X-11 ($$mass $$11.0093$$ amu, $$80.09\%$$ abundance). Calculate the atomic mass of element $$X.$$

Accepted Answer

$$10.81$$ amu

Question 11

Which law states that when two elements form two different compounds, the masses of one element that combine with a fixed mass of the other element are in a ratio of small whole numbers?

Accepted Answer

Law of multiple proportions

Question 12

Which subatomic particle is responsible for the identity of an element and is represented by the atomic number $$Z$$?

Accepted Answer

Proton

Question 13

A neutral atom of chlorine has an atomic number of $$17$$ and a mass number of $$35. $$How many neutrons does it have?

Accepted Answer

$$18$$

Question 14

Which of the following best describes the result of Rutherford’s gold foil experiment?

Accepted Answer

Most alpha particles passed through, but some were deflected at large angles.

Question 15

Which of the following is a property of nonmetals?

Accepted Answer

Poor conductor of heat

Question 16

How many atoms are present in $$75.0$$ grams of mercury ($$Hg$$)? (Atomic mass of $$Hg = 200.59 g/$$mol, Avogadro’s number $$= 6.02 	imes 10$$^{23}$$ atoms/mol)

Accepted Answer

$$2.25 	imes 10$$^{23}$$ atoms

Question 17

Which group on the periodic table contains elements that are highly reactive nonmetals, such as fluorine and chlorine?

Accepted Answer

Group 7A (halogens)

Question 18

Which of the following statements about ions is correct?

Accepted Answer

Cations are positively charged and formed by metals.

Question 19

Which of the following is a metalloid and is commonly used in the electronics industry due to its semiconductor properties?

Accepted Answer

Silicon

Question 20

If you have $$1.50$$ moles of sodium chloride ($$NaCl$$), how many formula units do you have? (Avogadro’s number $$= 6.02 	imes 10$$^{23}$$)

Accepted Answer

$$9.03 	imes 10$$^{23}$$

Atoms and Elements: Foundations of Modern Atomic Theory

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