Chapter 6 Chemical Composition

How many moles of Pb are in 4.71 x 10*21?

0.00782

What is the mass of 1.56 × 10*21 atoms of magnesium in grams?

0.0630

How many moles of bromine gas are in 37.7 grams?

0.236

How many moles are there in 17.5 grams of sodium?

0.761

How many hydrogen atoms are in 35.0 grams of hydrogen gas?

1.05 x 10*25

How many moles are there in 82.5 grams of iron?

1.48

How may atoms are in 1.50 moles of fluorine gas?

1.81 x 10*24

If a sample of carbon dioxide contains 3.8 moles of oxygen atoms, how many moles of carbon dioxide are in the sample?

1.9

One mole of boron has a mass of ________ g.

10.811

What is the mass percent of hydrogen in water?

11.2

An iron ore sample is found to be 35.00% Fe by mass. How many grams of ore are needed to obtain 454.0 of Fe?

1297

A 42.7 gram sample of potassium nitrate contains how many grams of potassium?

16.5

Calculate the molar mass of calcium nitrate

164.10 g/mol

You have 10.0 g each of Na, C, Pb, Cu and Ne. Which contains the largest number of moles?

C

What is the mass of 3.09 × 10*24 atoms of sulfur in grams?

165

How many moles of fluorine are in 3.2 moles of xenon hexafluoride?

19.2

An estrogen compound with the empirical formula C12H17O2 has a molecular mass of 386.6 g/mol. What is the value of n necessary to find the molecular formula?

2

One mole of ammonium nitrate contains:

2 moles of nitrogen

How many moles of Cu are in 1.48 x 10*25 Cu atoms?

24.6

What is the mass percent of carbon in oxalic acid, H2C2O4?

26.7

One half of a mole of atoms would contain how many atoms?

3.011 x 10*23

How many atoms are in 15.6 grams of silicon?

3.34 × 10*23

How many atoms are in 5.80 moles of He?

3.49 x 10*24

How many moles of carbon are in 3.5 moles of calcium carbonate?

3.5

How many moles of iron are contained in 1.75 kg of iron?

31.3

One mole of oxygen gas has a mass of ________ g.

32.0

What is the molar mass of aluminum sulfate?

342.2 g/mol

What is the mass in grams of 5.40 moles of lithium?

37.5

What is the mass of 0.560 moles of chlorine gas?

39.7

One mole of potassium sulfate contains

4 moles of oxygen

How many molecules of nitrogen monoxide are in a 22.5 gram sample?

4.51 x 10*23

If 3.011 x 10*23 molecules have a mass of 20.04 grams, what is the molar mass of the substance?

40.08 g/mol

The mass of one mole of carbon dioxide is ________ g.

44.01

A 500 gram iron ore sample was determined to contain 242 grams of iron. What is the mass percent of iron in the ore?

48.4

What is the value of n when the empirical formula is C3H5 and the molecular mass is 205.4 g/mol

5

How many molecules of sulfur trioxide are in 78.0 grams?

5.87 x 10*23

Bauxite is an ore that contains the element aluminum. If you obtained 108 grams of aluminum from an ore sample that initially weighed 204 grams, what is the mass percent of aluminum in this bauxite ore?

52.9

What is the correct value for Avogadros number?

6.022 × 10*23

A 15.5 gram sample of diphosphorous pentoxide contains how many grams of phosphorous?

6.76

One mole of (NH4)2HPO4 contains how many moles of hydrogen atoms?

9

Which of the following contains 9.02 x 10*23 atoms?

9.00 g H2O

Calculate the molar mass of ammonium carbonate?

96.09 g/mol

What is the mass percent of chlorine in hydrochloric acid?

97.2

A 7.96 gram sample of silver reacts with oxygen to form 8.55 gram of the metal oxide. What is the formula of the oxide?

Ag2O

One mole of ammonium nitrite contains

All of A, B, and C

Which of the following statement about empirical formula is incorrect?

An empirical formula represents a molecule

An unknown acid has a molar mass of 60.05 g/mol. Given the following percent composition, what is the molecular formula? 40% C, 6.7% H, 53.3% O

C2H4O2

Vitamin C is known chemically by the name ascorbic acid. Determine the empirical formula of ascorbic acid if it is composed of 40.92% carbon, 4.58% hydrogen, and 54.50% oxygen.

C3H4O3

Which of the following is already in its simplest formula?

C5H12O2

A compound has a molar mass of 180.18 g/mol. Given the following percent composition, calculate the molecular formula: 39.99% C, 6.73 %, H 53.28% O

C6H12O6

A compound composed of only carbon and hydrogen is 25.2% hydrogen by mass. The empirical formula for this compound is

CH4

Determine the correct empirical formula of a compound containing 26.68% carbon, 2.24% hydrogen, and 71.08% oxygen

CHO2

A chromium oxide compound contains 104.0 grams of chromium and 48.0 grams of oxygen. What is the most likely empirical formula of this compound?

Cr2O3

An iron chloride compound contains 55.85 grams of iron and 106.5 grams of chlorine. What is the most likely empirical formula for this compound?

FeCl3

A compound composed of only hydrogen and oxygen is 5.94% hydrogen by mass. The molar mass of this compound is 34.02 g/mol. What is the compounds molecular formula?

H2O2

Determine the empirical formula of a compound containing 83% potassium and 17.0% oxygen.

K2O

Determine the empirical formula of a compound containing 60.3% magnesium and 39.7% oxygen

MgO

Which of the following compounds has the highest mass percent of "O"?

MnO2

What is the molecular formula of a compound given the molar mass of the compound is 30.04 gram and the empirical formula is NH?

N2H2

What is the molecular formula of a compound given that molar mass of the compound is 186.5 Grams and the empirical formula is C2H7?

NONE OF THE ABOVE

If 2.01 x 10*23 atoms of an element from Group IA of the periodic table has a mass of 7.675 grams, this element is most likely

Na

Which of the following statement about the mole is FALSE?

One mole of water contains 1/2 mole of oxygen atoms

You have 10.0 g each of Na, C, Pb, Cu and Ne. Which contains the smallest number of moles?

Pb

In comparing a ballon containing 25 grams of helium to a balloon containing 25 grams of neon, which one of the following statements is TRUE?

The helium balloon has more atoms

In comparing 1 mole of carbon atoms to one mole of magnesium atoms, which statement is TRUE?

The mass of 1 mole of magnesium is greater than the mass of 1 mole of carbon.

The chemical formula CH2O can be classified as

empirical, possibly molecular.

The empirical formula of a compoud

indicates the simplest ratio of atoms in the compoud

What would the empirical formula be for the molecular compound C6H9O4?

none of the above

The simplest formula for hydrogen peroxide is HO. To determine its molecular formula, it is necessary to know

the molar mass of hydrogen peroxide