Question 1

A sample of pure calcium fluoride with a mass of 15.0 g contains 7.70 g of calcium.How much calcium is contained in 35.0 g of calcium fluoride?

Accepted Answer

We can use the ratio of calcium to calcium fluoride in the sample to calculate the amount of calcium in 35.0 g of calcium fluoride.
First, we need to find the amount of calcium fluoride in the sample:
mass of calcium fluoride = mass of sample - mass of calcium
mass of calcium fluoride = 15.0 g - 7.70 g
mass of calcium fluoride = 7.30 g
Now we can set up a proportion:
mass of calcium / mass of calcium fluoride = x / 35.0 g
where x is the amount of calcium in 35.0 g of calcium fluoride.
Solving for x, we get:
x = (mass of calcium / mass of calcium fluoride) * 35.0 g
x = (7.70 g / 7.30 g) * 35.0 g
x = 37.0 g
Therefore, 35.0 g of calcium fluoride contains 18.0 g of calcium. The correct answer is D.

Question 2

Which of the following elements is classified as a semimetal?

Accepted Answer

Astatine is classified as a semimetal or a metalloid due to its intermediate properties between metals and nonmetals. Gold, osmium, and berkelium are all classified as metals.

Question 3

All of the following elements are nonmetals except

Accepted Answer

Copper is a metal. Therefore, A is the only choice that is a nonmetal.

Question 4

Which of the following represent isotopes? A:  [ ] B:  [ ] C:  [ ] D:  [ ]

Accepted Answer

The answer of Which of the following represent isotopes? A:...

Question 5

Sodium metal and water react to form hydrogen and sodium hydroxide.If 11.96 g of sodium react with water to form 0.52 g of hydrogen and 20.80 g of sodium hydroxide,what mass of water was involved in the reaction?

Accepted Answer

The mass of water involved can be found using the law of conservation of mass, which states that mass is neither created nor destroyed in a chemical reaction. The total mass of reactants equals the total mass of products. The mass of sodium (11.96 g) plus the mass of water gives the mass of hydrogen (0.52 g) plus the mass of sodium hydroxide (20.80 g). To find the mass of water, subtract the mass of sodium, hydrogen, and sodium hydroxide from the total mass: (0.52 g + 20.80 g) - 11.96 g = 9.36 g.

Question 6

What is the element symbol for an atom that has 33 protons and 41 neutrons?

Accepted Answer

The element with 33 protons is arsenic (As). The number of neutrons does not affect the element symbol, only the atomic number (number of protons) does.

Question 7

Which of the following elements is a good conductor of heat and electricity?

Accepted Answer

Lead is a known good conductor of both heat and electricity, making it a popular material for electrical wiring, batteries, and car engines. Silicon is used for making semiconductors but does not conduct electricity as well as lead. Iodine and radon are nonmetals and poor conductors of heat and electricity.

Question 8

Which are isotopes? An atom that has an atomic number of 35 and a mass number of 76 is an isotope of an atom that has

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons. The atom mentioned in the question has an atomic number of 35, which means it has 35 protons. However, it has a mass number of 76, which means it has 41 neutrons. The only other option with an atomic number of 35 is (B), which has a different mass number of 80, indicating it is a different isotope of the same element. Option (A) has a different atomic number and the same mass number, making it a different element. Option (C) and (D) provide additional information about the composition of the atom but do not help to identify which other atom it is an isotope of.

Question 9

Which of the following elements is not a solid at room temperature?

Accepted Answer

The answer of Which of the following elements is not...

Question 10

A proton is approximately

Accepted Answer

A proton is approximately 2000 times more massive than an electron, not larger in terms of physical size. This comparison refers to mass, not spatial dimensions.

Question 11

A sample of pure lithium chloride contains 16% lithium by mass.What is the % lithium by mass in a sample of pure lithium carbonate that has twice the mass of the first sample?

Accepted Answer

In the first sample, if the total mass is 100 g, then the mass of lithium is 16 g. Therefore, the mass of chloride is 84 g.

In the second sample, if the mass of lithium chloride is 2x g, then the mass of lithium in it is 0.16 x 2x = 0.32x g.

Now we need to find what % is 0.32x g of the total mass of lithium carbonate which is twice the mass of lithium chloride, i.e. 2 x 100 = 200 g.

Let the mass of lithium carbonate be 200 g. Then, the mass of lithium in it is 0.16 x 200 = 32 g.

Therefore, % lithium by mass in lithium carbonate sample = (32/200) x 100 = 16%.

So the answer is B, 16.4%.

Question 12

How many protons (p)and neutrons (n)are in an atom of calcium-46?

Accepted Answer

Calcium has an atomic number of 20, which means it has 20 protons. The atomic mass of calcium-46 is given as 46, which means it must have 46 - 20 = 26 neutrons. Thus, the correct answer is A) 20 p, 26 n.

Question 13

Mg can react with HCl to produce the white solid MgCl₂ and H₂ gas.A student mixes 1.99 g of Mg with 5.98 g of HCl.If the mass of the white solid is 7.79 g,then what is the mass of H₂ produced?

Accepted Answer

We need to first find the limiting reactant to determine how much H₂ gas is produced. Mg + 2HCl -> MgCl2 + H2 Using stoichiometry, we can find that 1 mole of Mg reacts with 2 moles of HCl producing 1 mole of H2 gas. The moles of Mg given: 1.99g / 24.31 g/mol = 0.0819 mol The moles of HCl given: 5.98g / 36.46 g/mol = 0.164 mol Since there are fewer moles of Mg, it is the limiting reactant. Therefore, all of the Mg will react, and the amount of H₂ gas produced will be determined by the amount of HCl left over after the reaction. Mg + 2HCl -> MgCl2 + H2 0.0819 mol Mg * 2 mol HCl / 1 mol Mg = 0.164 mol HCl required 0.164 mol HCl - 0.164 mol HCl given = 0 moles of HCl left over Therefore, all of the HCl is used up in the reaction, and there is no H₂ gas produced. The only product is the white solid MgCl2, which has a mass of 7.79 g. The mass of H₂ produced is 0.0 g. Therefore, the best choice is B with the explanation provided.

Question 14

Which one of the following elements is a poor conductor of heat and electricity?

Accepted Answer

Sulfur is a non-metal and therefore a poor conductor of both heat and electricity.

Question 15

Identify the chemical symbol of element Q in  Q.

Accepted Answer

The answer of Identify the chemical symbol of element Q...

Question 16

How many protons (p)and neutrons (n)are in an atom of  Ra?

Accepted Answer

The answer of How many protons (p)and neutrons (n)are in...

Question 17

The isotope represented by ^{C is named}

Accepted Answer

The answer of The isotope represented by  <sup>C is...

Question 18

How many electrons are in a neutral atom of iodine-131?

Accepted Answer

In a neutral atom, the number of electrons equals the number of protons. Iodine (I) has an atomic number of 53, indicating it has 53 protons and, therefore, 53 electrons in its neutral state.

Question 19

Methane and oxygen react to form carbon dioxide and water.What mass of water is formed if 6.4 g of methane reacts with 25.6 g of oxygen to produce 17.6 g of carbon dioxide?

Accepted Answer

The balanced chemical equation for the reaction is:
CH4 + 2O2 → CO2 + 2H2O

Using the given masses we can calculate the limiting reagent:
Moles of methane = 6.4 g / 16.04 g/mol = 0.4 mol
Moles of oxygen = 25.6 g / 32.00 g/mol = 0.8 mol

From the balanced equation, 1 mole of methane reacts with 2 moles of oxygen to produce 2 moles of water.
So, 0.4 mol of methane reacts with 0.8 mol of oxygen to produce 0.8 mol of water.

Moles of water = 0.8 mol
Mass of water = moles of water × molar mass of water
= 0.8 mol × 18.02 g/mol
= 14.416 g ≈ 14.4 g

Therefore, the mass of water formed is 14.4 g. Hence the correct choice is A.

Question 20

Which are isotopes? An atom that has an atomic number of 12 and a mass number of 26 is an isotope of an atom that has

Accepted Answer

Isotopes are atoms with the same atomic number (same number of protons) but different mass numbers (different number of neutrons). An atom with an atomic number of 12 and a mass number of 24 has the same number of protons but a different number of neutrons compared to the atom with a mass number of 26.

Quiz 2: Atoms, molecules, and Ions

A sample of pure calcium fluoride with a mass of 15.0 g contains 7.70 g of calcium.How much calcium is contained in 35.0 g of calcium fluoride?

Which of the following elements is classified as a semimetal?

All of the following elements are nonmetals except

Which of the following represent isotopes? A: [ ] B: [ ] C: [ ] D: [ ]

Sodium metal and water react to form hydrogen and sodium hydroxide.If 11.96 g of sodium react with water to form 0.52 g of hydrogen and 20.80 g of sodium hydroxide,what mass of water was involved in the reaction?

What is the element symbol for an atom that has 33 protons and 41 neutrons?

Which of the following elements is a good conductor of heat and electricity?

Which are isotopes? An atom that has an atomic number of 35 and a mass number of 76 is an isotope of an atom that has

Which of the following elements is not a solid at room temperature?

A proton is approximately

A sample of pure lithium chloride contains 16% lithium by mass.What is the % lithium by mass in a sample of pure lithium carbonate that has twice the mass of the first sample?

How many protons (p) and neutrons (n) are in an atom of calcium-46?

Mg can react with HCl to produce the white solid MgCl₂ and H₂ gas.A student mixes 1.99 g of Mg with 5.98 g of HCl.If the mass of the white solid is 7.79 g,then what is the mass of H₂ produced?

Which one of the following elements is a poor conductor of heat and electricity?

Identify the chemical symbol of element Q in Q.

How many protons (p) and neutrons (n) are in an atom of Ra?

The isotope represented by ^{C is named}

How many electrons are in a neutral atom of iodine-131?

Methane and oxygen react to form carbon dioxide and water.What mass of water is formed if 6.4 g of methane reacts with 25.6 g of oxygen to produce 17.6 g of carbon dioxide?

Which are isotopes? An atom that has an atomic number of 12 and a mass number of 26 is an isotope of an atom that has

Quiz 2: Atoms, molecules, and Ions

A sample of pure calcium fluoride with a mass of 15.0 g contains 7.70 g of calcium.How much calcium is contained in 35.0 g of calcium fluoride?

Which of the following elements is classified as a semimetal?

All of the following elements are nonmetals except

Which of the following represent isotopes? A: [ ] B: [ ] C: [ ] D: [ ]

Sodium metal and water react to form hydrogen and sodium hydroxide.If 11.96 g of sodium react with water to form 0.52 g of hydrogen and 20.80 g of sodium hydroxide,what mass of water was involved in the reaction?

What is the element symbol for an atom that has 33 protons and 41 neutrons?

Which of the following elements is a good conductor of heat and electricity?

Which are isotopes? An atom that has an atomic number of 35 and a mass number of 76 is an isotope of an atom that has

Which of the following elements is not a solid at room temperature?

A proton is approximately

A sample of pure lithium chloride contains 16% lithium by mass.What is the % lithium by mass in a sample of pure lithium carbonate that has twice the mass of the first sample?

How many protons (p) and neutrons (n) are in an atom of calcium-46?

Mg can react with HCl to produce the white solid MgCl2 and H2 gas.A student mixes 1.99 g of Mg with 5.98 g of HCl.If the mass of the white solid is 7.79 g,then what is the mass of H2 produced?

Which one of the following elements is a poor conductor of heat and electricity?

Identify the chemical symbol of element Q in Q.

How many protons (p) and neutrons (n) are in an atom of Ra?

The isotope represented by C is named

How many electrons are in a neutral atom of iodine-131?

Methane and oxygen react to form carbon dioxide and water.What mass of water is formed if 6.4 g of methane reacts with 25.6 g of oxygen to produce 17.6 g of carbon dioxide?

Which are isotopes? An atom that has an atomic number of 12 and a mass number of 26 is an isotope of an atom that has

Mg can react with HCl to produce the white solid MgCl₂ and H₂ gas.A student mixes 1.99 g of Mg with 5.98 g of HCl.If the mass of the white solid is 7.79 g,then what is the mass of H₂ produced?

The isotope represented by ^{C is named}