Ch 5 and 6

What is the mass of 1.56 × 1021 atoms of magnesium in grams? 4.72 × 10-5 0.0630 1.07 × 10-4 0.142 none of the above

0.0630

How many moles are there in 17.5 grams of sodium? 1.05 × 1025 1.31 22.99 0.761 none of the above

0.761

How many atoms are in 1.50 moles of fluorine gas? 1.81 × 1024 6.022 × 1023 18.98 9.03 × 1023 none of the above

1.81

One mole of boron has a mass of ________ g. 6.022 × 1023 9.012 10.811 5 none of the above

10.811

What is the formula mass of copper(II) fluoride? none of the above 90.00 101.55 146.10 165.10

101.55

What is the formula mass for diboron tetrachloride? 234.34 amu none of the above 163.43 amu 198.89 amu 127.98 amu

163.43 amu

How many atoms are present in 4.5 moles? 6.02 × 1023 3.7 × 10-25 2.7 × 1024 3.7 × 1023 none of the above

2.7 × 1024

How many atoms are in 15.6 grams of silicon? 0.555 3.34 × 1023 2.64 × 1026 438 none of the above

3.34 × 1023

How many atoms are in 5.80 moles of He? 3.49 × 1024 6.02 × 1023 1.03 × 1023 4.00 You Answered none of the above

3.49 × 1024

How many molecules of nitrogen monoxide are in a 22.5 gram sample? 4.51 × 10^23 7.33 × 10^23 4.06 × 10^23 5.86 × 10^23 none of the above

4.51 × 1023

A 500. gram iron ore sample was determined to contain 242 grams of iron. What is the mass percent of iron in the ore? 32.6 48.4 51.6 93.7 none of the above

48.4

The charge of a vanadium ion in the compound V2O5 is: 5+ none of the above 10- 10+ 2+

5+. The charge of oxygen ion is: -2 (negative)The total charge of the compound must be 0, so:The charge of vanadium ion: ((-2) ∙ 5) / 2 = +5 (must be positive)Answer:+5

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? 0.53 52.9 47.1 15.6 none of the above

52.9

One hundred nickels must have the same mass as one hundred pennies. True False

False

One mole of zinc contains 65.39 zinc atoms. True False

False

The chemical formula clearly indicates the relationship between the mass of each element in the formula

False

The number 6.022 × 1023 is six times larger than the number 6.022 × 1022. True False

False

The empirical formula mass must be 25.0 if the molecular formula mass is 250 and n = 5. True False

False If empirical formula mass is 25 and molecular formula mass is 250 , then n = Molecular formula mass/ Empircal formula mass = 10

The mole has a value of 6.023 × 1022. True False

False = 6.022 x 10^23

SO2 is an ionic compound.

False it is a molecular compound = covalant

The subscripts in a chemical formula represent the relative mass of each atom in a chemical compound.

False- The subscripts does not represent the relative mass of each type of atom in the compound, it represents relative number of atoms

The proper name for SF6 is sulfur tetrafluoride.

False. It is Sulfur hexafluoride

The correct formula for calculating mass percent of X in compound X/Y is: = Mass of X in sample of a compound/ Mass of Y in a sample of a compound Mass % X True False

False. The mass percent of X = mass of X in a sample of the compound/ mass of the sample compound.

What is the formula for an ionic compound made of magnesium and sulfur? none of the above MgS MgS2 Mg2S3 Mg2S

MgS

Avogadro's Number is 6.022 × 1023. True False

True

C2H6O3 could be an empirical formula. True False

True

Mass is used as a method of counting atoms

True

One mole of I2 has more atoms in it than one mole of Na.

True

One mole of nitrogen gas contains (2) × (6.022 × 1023) nitrogen atoms.

True

One mole of water contains 16 grams of oxygen atoms. True False

True

The basic unit of an ionic compound is called the formula unit.

True

The law of constant composition states: All samples of a given compound have the same proportions of their constituent elements.

True

The lighter the atom, the less mass in one mole of that atom.

True

Two moles of cobalt atoms have a mass of 117.87 grams. True False

True

Six grams of carbon contains 3.008 × 1023 atoms.

True Mass of C-atoms = 6g No.of moles =mass/molar mass= 6/12=0.5moles No. Of atoms moles*Avagadro no. =0.5*6.022*10^-35=3.011*10^-35 So 3.011*10^-35 atoms are in 6g of C atoms.

Which statement is always true for samples of atomic elements, regardless of the type of element present in the samples? a. If two samples of different elements have the same mass, they contain the same number of atoms. b. If two samples of different elements contain the same number of atoms, they contain the same number of moles. c. If two samples of different elements have the same mass, they contain the same number of moles.

b. If two samples of different elements contain the same number of atoms, they contain the same number of moles. The mole is a counting unit; it represents a definite number (Avogadro's number, 6.022 × 1023). Therefore, a given number of atoms always represents a precise number of moles, regardless of what atom is involved. Atoms of different elements have different masses. So if samples of different elements have the same mass, they cannot contain the same number of atoms or moles.

Without doing any calculations, determine which sample contains the most atoms. a. one gram of lead b. one gram of carbon c. one gram of cobalt

b. one gram of carbonBecause carbon has lower molar mass than cobalt or lead, a 1-g sample of carbon contains more atoms than 1 g of cobalt or lead. molar mass of the sample increases then the number of moles decreases and moles also decreases. Smaller the amu the most atoms

What is the name of the ionic compound made of beryllium and chlorine? beryllium(II) chloride none of the above monoberyllium dichloride beryllium chloride beryllium dichloride

beryllium chloride