Chapter One
For each pair, which has the higher potential energy?
(a) The fuel in your car of the gaseous products in its exhaust
(b) Wood in a fire or the gaseous products in its exhaust
(a) fuel
(b) wood
2.16
Does the mass of each element in a compound depend on the amount of compound?
Yes
3.2
How many moles of C atoms are in 1 mol of sucrose (C12 H22 O11)?
12 mol C atoms
4.14
Is each of the following very soluble in water?
(a) Benzene, C6H6
(b) sodium hydroxide
(c) ethanol, CH3CH2OH
(d) potassium acetate
(a) insoluble
(b) very soluble
(c) soluble
(d) ionic, very soluble
4.67
Limestone (calcium carbonate) is insoluble in water but dissolves in aqueous hydrochloric acid. Write balanced total ionic and net ionic equations, showing hydrochloric acid as it actually exists in water and the reaction as a proton-transfer process.
La Check book
The average radius of a molecule of lysozyme, an enzyme in tears, is 1430 pm. What is its radius in nanometers (nm)?
1.43 nm
2.12
To which class(es) of matter--elements, compounds, and/or mixtures--do the following apply: (a) law of mass conservation; (b) law of definite composition; (c) law of multiple proportions?
(a) elements, compounds, and mixtures
(b) compounds
(c) compounds
Calculate the number of Ca atoms in 28.5 g of Ca
4.28*10^23 Ca atoms
4.2
What types of substances are most likely to be soluble in water?
Ionic or polar covalent compounds
4.47
If 38.5 mL of lead(II) nitrate solution reacts completely with excess sodium iodide solution to yield 0.628 g of precipitate, what is the molarity of lead(II) ion in the original solution?
0.0354 M Pb 2+
Calculate the following equation, giving an answer with the correct amount of significant figures:
1.110 cm + 17.3 cm +108.2 cm + 316 cm
443 cm
2.20
Fluorite, a mineral of calcium, is a compound of the metal with fluorine. Analysis shows that a 2.76 g sample of fluorite contains 1.42 g of calcium. Calculate (a) the mass of fluorine in the sample; (b) mass fractions of calcium and fluorine in fluorite; (c) mass percents of calcium and fluorine in fluorite
(a) 1.34 g
(b) 0.514 Ca; 0.486 F
(c) 51.4 mass % Ca; 48.6 mass % F
Iron reacts slowly with oxygen and water to form a compound commonly called rust (Fe2 O3 * 4 H2O). For 45.2 kg of rust, calculate (a) moles of compound; (b) moles of Fe2O3
(a) 195 mol of compound
(b) 195 mol Fe2O3
4.18
How many total moles of ions are released when each of the following dissolves in water?
(a) 0.32 mol NH4Cl
(b) 25.4 g of Ba(OH)2*H2O
(a) 0.64 mol
(b) 0.242 mol
4.53
A 1.50-g sample of an unknown alkali-metal carbonate was dissolved in water, and 31.10 mL of 0.350M CaCl2 was required to precipitate all the carbonate ions as CaCO3. Give the name and formula of the unknown compound.
Potassium carbonate, K2CO3
Which of the following properties are intensive?
-Mass - Density - Volume - Melting Point
Density and Melting Point
2.36
Define atomic number and mass number.
Which can vary without changing the identity of the element?
The atomic number is the number of protons in an atom's nucleus. When the atomic number changes, the identity of the element changes. The mass number is the total number of protons and neutrons in the nucleus. The mass number can vary (by a change in the number of neutrons) without changing the identity of the element.
3.44
An oxide of nitrogen contains 30.45 mass % N.
(a) What is the empirical formula of the oxide?
(b) If the molar mass is 90 +/-5 g/mol, what is the molecular formula?
(a) NO2
(b) N2O4
Muriatic acid, an industrial grade of concentrated HCL, is used to clean masonry and cement. Its concentration is 11.7 M.
Write instructions for diluting the concentrated acid to make 3.0 gallons of 3.5 M acid for routine use (1 gal = 4 qt; 1 qt = 0.946 L). Answer must be in units of gallons.
Pour approx. 2 gallons of water into the container. Add 0.90 gallons of concentrated HCl. Dilute to 3.0 gallons with more water.
1.72
A lab instructor gives a sample of amino-acid powder to Student 1, Student 2, Student 3, and Student 4, and they weigh the samples. The true value is 8.72 g. Their results for three trials are:
S1: 8.72 g, 8.74 g, 8.70 g
S2: 8.56 g, 8.77 g, 8.83 g
S3: 8.50 g, 8.48 g, 8.51 g
S4: 8.41 g, 8.72 g, 8.55 g
(a) Calculate the average mass from each set of data, and tell which set is the most accurate
(b) Which set of data is the most precise?
(c) Which set of data is both the most accurate and the most precise?
(a) Student 1 average = 8.72 g; Student 2 average = 8.72 g; Student 3 average = 8.50 g; Student 4 average = 8.56 g; sets one and two are most accurate
(b) Set 3 is the most precise but is the least accurate
(c) Set 1 has both high accuracy and high precision
Chlorine has two naturally occurring isotopes, Cl-35 (isotopic mass = 34.9689 amu) and Cl-37 (isotopic mass = 36.9659 amu). If chlorine has an atomic mass of 35.4527 amu, what is the percent abundance of each isotope?Cl
Cl-35 = 75.774 %, Cl-37 = 24.226 %
3.48
Menthol (M = 156.3 g/mol), the strong-smelling substance in many cough drops, is a compound of carbon, hydrogen, and oxygen. When 0.1595 g of menthol was burned in a combustion apparatus, 0.449 g of CO2 and 0.184 g of H2O formed. What is menthol's molecular formula?
C10 H20 O
4.36
Which ions do not appear in a net ionic equation, and why?
Spectator ions do not appear in a net ionic equation because they are not involved in the reaction and serve only to balance charges