FINAL EXAM CHEM 101 Questions
Balance the following chemical reaction: Al₂(SO₄)₃ (aq) + K₃PO₄ (aq) → AlPO₄ (s) + K₂SO₄ (aq) A) Al₂(SO₄)₃ (aq) + 2 K₃PO₄ (aq) → 2 AlPO₄ (s) + 3 K₂SO₄ (aq) B) 2 Al₂(SO₄)₃ (aq) + 6 K₃PO₄ (aq) → 3 AlPO₄ (s) + 6 K₂SO₄ (aq) C) 2 Al₂(SO₄)₃ (aq) + 4 K₃PO₄ (aq) → 4 AlPO₄ (s) + 6 K₂SO₄ (aq) D) AlSO₄ (aq) + KPO₄ (aq) → AlPO₄ (s) + KSO₄ (aq)
A) Al₂(SO₄)₃ (aq) + 2 K₃PO₄ (aq) → 2 AlPO₄ (s) + 3 K₂SO₄ (aq) Solution: Matter is conserved in a chemical reaction. Balanced equations contain the same number of atoms of each element on each side of the equation. For example, in this chemical equation: Al₂(SO₄)₃ (aq) + 2 K₃PO₄ (aq) → 2 AlPO₄ (s) + 3 K₂SO₄ (aq), there are 2 Al atoms, 3 S atoms, 20 O atoms, 6 K atoms, and 2 P atoms on the reactant side. There are 2 Al atoms, 2 P atoms, 20 O atoms, 3 S atoms, and 6 K atoms on the product side. These numbers are equal on both sides.
Which has the correct name-formula combination? A) Barium oxide - BaO B) Lithium nitride - LiN C) Aluminum sulfide - AlS D) Rubidium phosphide - RbP
A) Barium oxide - BaO Solution: Consider the charge of the ions to make sure the charges are balanced. Barium forms ions with a +2 charge and oxygen forms ions with a -2 charge. The ionic formula would be BaO. Consider the charge of the ions to make sure the charges are balanced.
The compound NaBr is: A) Ionic B) Polar covalent C) Nonpolar covalent D) Metallic E) Not enough info
A) Ionic
Quicklime, CaO, is an important substance used in making mortar. What kind of bonds are present in this compound? A) ionic B) covalent C) metallic D) coordinate
A) ionic Solution: The ionic bond in this compound forms between the Ca²⁺ cation and the O²⁻ anion.
The uncertainty in the measurement 80.2 g is A) ± 0.1 g B) ± 1 g C) ± 0.01 g D) ± 10 g
A) ± 0.1 g Solution: The last significant digit of a measurement is uncertain and its place value is used in the uncertainty. For example, the 2 in the tenths place in 80.2 is uncertain, yielding an uncertainty measurement of ± 0.1.
Which atom in the Br-F molecule has a partial positive charge (δ⁺)? A) Br B) F C) Both D) Neither
A.) Br solution: Partial charges are determined by the relative electronegativities of the atoms in a molecule; the less electronegative atom, which is Br, has a partial positive charge.
Which of the following represents the intermolecular forces present in CO₂? A) dispersion only B) dipole-dipole only C) hydrogen bonding only D) dispersion and dipole-dipole E) dispersion and hydrogen bonding
A.) dispersion only solution: CO₂ does not have any hydrogen atoms, so it cannot exhibit hydrogen bonding. While CO₂ has two internal dipoles, they are of equal magnitude and point in opposite directions, meaning they cancel each other out and the molecule has no net dipole moment, so it cannot exhibit dipole-dipole forces. The only intermolecular forces it will exhibit are dispersion forces, which are exhibited by all species with electrons.
Which of the following compounds contains a metal? A) CO₂ B) LiCl C) H₂O D) CH₄ E) PBr₃
B) LiCl Solution: Lithium chloride is a salt, comprised of an alkali metal (lithium) cation and a halide (chloride) anion.
Which of the following reactions is an acid-base reaction? A) AgNO₃(aq) + KF(aq) → AgF(s) + KNO₃(aq) B) NH₃(aq) + HF(aq) → NH₄⁺(aq) + F⁻(aq) C) NO₂⁻(aq) + Al(s) → NH₃(g) + AlO₂⁻(aq) D) CH₄(g) + 2O₂(g) → 2H₂O(g) + CO₂(g)
B) NH₃(aq) + HF(aq) → NH₄⁺(aq) + F⁻(aq) solution: NH₃(aq) + HF(aq) → NH₄⁺(aq) + F⁻(aq) is an acid-base reaction. It involves the transfer of a proton from one species (the acid, in this case HF) to another (the base, in this case NH₃).
Single, double, or triple covalent bonds in a carbon atom are formed from A) inner shell electrons B) valence electrons. C) both inner shell and valence electrons.
B) valence electrons.
How many neutrons are in an atom of uranium-235? A) 92 B) 143 C) 235 D) 238.0
B.) 143 Solution: Uranium-235 has a mass of 235. Uranium always has 92 protons. Therefore, uranium-235 has 143 neutrons.
What volume of 0.220 M HBr solution (in mL) is required to obtain 0.0600 moles of HBr? A) 3.67 L B) 273 mL C) 2.73 x 10⁻⁴ mL D) 13.2 mL
B.) 273 mL (0.0600 mol/1) x (1 L/0.220 mol) x (1000 mL/1 L) =273 mL
Which one of the following would be a chemical property of a sample of neon gas? A) It is a gas at room temperature. B) It is inert. C) It is colorless. D) It boils at -246 °C.
B.) It is inert. Solution: If a property (being inert) can not be measured without chemically changing the substance, it's a chemical property.
Which atom in the O-C single bond has a partial negative charge (δ⁻)? A) C B) O C) Both D) Neither
B.) O solution: Partial charges are determined by the relative electronegativities of the atoms in a bond; the more electronegative atom, which is O, has a partial negative charge.
Which particle(s) may be found in the nucleus of an atom? A) Proton and electron B) Proton and neutron C) Proton only D) Neutron only E) Neutron and electron
B.) Proton and neutron Solution: Protons and neutrons are found in the nucleus of an atom.
Which has the correct name-formula combination? A) Chlorine pentafluoride - ClF B) Diphosphorus pentoxide - P₂O C) Carbon tetraiodide - CI₄ D) Sulfur tetrafluoride - SF
C) Carbon tetraiodide - CI₄ Solution: Consider the prefix and the number of atoms it indicates. For example, the prefix tetra- in carbon tetraiodide indicates that there are four iodine atoms.
Which one of the following would be a physical property of glucose? A) It is used by the body to generate energy. B) When combined with sulfuric acid it forms carbon. C) In its pure form, it is a white powder. D) It can be fermented to form ethanol.
C) In its pure form, it is a white powder. Solution: If a property (being a white powder) can be measured without chemically changing the substance, it's a physical property.
Some liquid in a jar can be separated by physical means into two separate liquids, which can then be separated no further. The liquid is a(n): A.) Compound B.) Element C.) Mixture D.) Pure Substance
C.) Mixture Solution: If a sample of matter (the liquid in the jar) can be separated by physical means, it's a mixture. Otherwise, it's a pure substance that can either be an element or compound.
Predict the chemical formula for the ionic compound formed by the elements Ca and Br
CaBr2
Which of the following numbers contains four significant figures? A) 1561.0 B) 0.053 C) 0.761 D) 3.101 E) 1400
D) 3.101 Solution: Count the number of significant figures in each option. Be sure to account for non-zero digits, zeros found between two significant digits, and zeros following a significant digit in a decimal. Leading zeros and trailing zeros without a decimal point are not significant. The value 3.101 contains four significant figures.
How many electrons are shared between two atoms in a triple bond? A) 2 B) 3 C) 4 D) 6
D) 6
Which of the following halogens would have the highest boiling point? A) F₂ B) Cl₂ C) Br₂ D) I₂
D) I₂ solution: The boiling point is the temperature at which a substance will change from the liquid phase to the gas phase, so compounds with stronger intermolecular forces will have higher boiling points. Since all of these options are nonpolar, their only intermolecular forces are dispersion forces, which are higher for molecules with more electrons, which can be dispersed. Of these options, I₂, has the most electrons, so it has the strongest intermolecular forces and therefore the highest boiling point.
Which has the correct name-formula combination? A) Iron(II) nitride - FeN B) Nickel(II) oxide - NiO₂ C) Titanium(IV) phosphide - TiP D) Manganese(II) sulfide - MnS
D) Manganese(II) sulfide - MnS Solution: Consider the charge of the ions to make sure the charges are balanced. For the transition metals, the charge is indicated in the name with a Roman numeral in parentheses. For example, manganese(II) sulfide indicates that the manganese ion has a +2 charge. Sulfide has a -2 charge. The formula for manganese(II) sulfide would be MnS.
Which one of the following is NOT an example of a physical change? A) distilling water to remove impurities B) filtration of sand out of water C) mixing water and sugar D) electrolysis of water to form hydrogen and oxygen gas.
D) electrolysis of water to form hydrogen and oxygen gas. Solution: In a chemical change, one substance must be converted into another. In electrolysis, the chemical bonds in water are broken to release elemental hydrogen and oxygen as gases.
Which one of the following statements is FALSE? A) Ionic bonding results from the transfer of electrons from one atom to another B) Dipole moments result from the unequal distribution of electrons in a molecule C) The electrons in a polar bond are found nearer to the more electronegative element D) A molecule with very polar bonds can be nonpolar E) Linear molecules cannot have a net dipole moment
E) Linear molecules cannot have a net dipole moment solution: Linear molecules can easily be polar given the appropriate arrangement of elements. Draw the Lewis structure for HCN for an example.
Determine the formula weight of NH₄Br. Provide an answer to two decimal places.
N-14.01 , H-1.01 (4) 4.01 , Br-79.80 =98 amu
Write the basic equilibrium equation for NH₃
NH3 (aq) + H2O (l) = NH4+ (aq) + OH- (aq)
Predict the chemical formula for the ionic compound formed by V³⁺ and NO₂⁻
V(NO2)3
What volume in mL of 0.300 M NaF would be required to make a 0.0410 M solution of NaF when diluted to 250.0 mL with water? V1C1=V2C2
V1 (0.300 M)= (250.0 mL) (0.0410 M) V1 (0.300 M)=10.25 mL / 0.300 M. 0.300 M =34.17 ---> 34.2 mL v1= 34.2 mL
What type of reaction is represented by the following equation: KOH(aq) + NH₄Cl(aq) → NH₃(aq) + KCl(aq) + H₂O(l) A) acid-base B) decomposition C) precipitation D) redox (oxidation-reduction)
a.) acid base solution: This is an acid-base reaction, which involves the transfer of a proton from one species (the acid, in this case NH₄⁺) to another (the base, in this case OH⁻).
How many electrons are in a neutral ⁴¹Ca atom? A) 2 B) 20 C) 21 D) 41
b.) 20 Solution: Calcium has 20 protons. Therefore a neutral calcium atom has 20 electrons.
How many protons are in an atom of strontium-90? A) 2 B) 38 C) 87.62 D) 90
b.) 38 Solution: Strontium has an atomic number of 38. The atomic number is the number of protons in an atom.
Which one of the following is an example of a heterogeneous mixture? A) coffee B) water C) sand D) tap water
c.) Sand Solution: If a sample of matter is a mixture that is not uniform in composition, it's a heterogeneous mixture. Sand does not have a uniform composition.
Ammonia and hydrogen fluoride both have unusually high boiling points due to _____ A) dispersion forces. B) dipole-dipole interactions. C) hydrogen bonding. D) ion-dipole interactions. E) low molar masses.
c.) hydrogen bonding solution: High boiling points are a consequence of strong intermolecular forces. Because ammonia (NH₃) and hydrogen fluoride (HF) both have high boiling points, they must have strong intermolecular forces. Each of these compounds contains an H atom directly bonded to one of the highly electronegative N, O, or F atoms, so their high boiling points result from their hydrogen bonding.
How many moles of ammonia would be required to react exactly with 0.840 moles of copper(II) oxide in the following chemical reaction? 2 NH₃(g) + 3 CuO(s) → 3 Cu(s) + N₂(g) + 3 H₂O(g)
(0.840 mol CuO/1) x (2 mol NH3/3mol CuO) =0.560 mol
What is the mass in grams of 2.50 gal of water? The density of water is 1.00 g/mL
(2.50 gal/1) x (3.785 L/1 gal) x (1,000mL/1L)x (1.00g/1 mL) = 9.46x10^3
The density of helium in a balloon is 1.18 g/L. If a balloon holds 2.83 L of He, how many atoms of He are in the balloon?
(2.83L/1) x (1.18 g/1L) x (1 mol/3.34 g) x (6.02x10^23 atoms/1 mol) = 5.02 x 10^23 atoms
If 0.112 moles of NaCl are dissolved in a 250.0 mL solution, what is the concentration of the NaCl solution?
(250.0 mL/1) x (1 L/1000 mL) = 0.25 L (0.112 mol/ 0.25 L) = 0.448 M
Determine the number of atoms in 30.0 g of S.
(30g/1) x (1 mol/32.07 g) x (6.02x10^23 atoms/1 mol) = 5.63x10^23 atoms
A particular medication dosage is 45.0 mg/kg of body weight. What is the mass in mg of the medication a child weighing 62.7 lb. should receive?
(62.7lb/1) x (1 Kg/2,2046 lb) x (45.0mg/1Kg)= 1,281 mg
What is the mass in grams of magnesium chloride that can be produced from 9.31 moles of chlorine gas reacting with excess magnesium? Mg(s) + Cl₂(g) → MgCI₂(s)
(9.31 mol Cl2/1) x (1 mol MgCl2/1 mol Cl2) x (95.21 g MgCl2/1 mol MgCl2) =886.4 g **Find mass of Mg and Cl2 then add them up to get 95.21 g
What is the pH of a 0.00765 M solution of HCl? ph= -log [H3O+]
-log (0.00765) =2.1
An irregularly-shaped piece of aluminum (Al) has a mass of 57.7 grams. What is the volume in cm³ of this piece of aluminum if its density is 2.70 g/cm³? (V=Mass/Density)
21.37 -----> 21.4 cm³
The number 98000 written in scientific notation would be A) 9.8 × 10⁴ B) 9.8 × 10⁻⁴ C) 9.8 × 10³ D) 9.8 × 10⁻⁵
A) 9.8 × 10⁴ Solution: When converting a number to scientific notation, the decimal place is moved once for each power of 10 in the original number to leave only one number before the decimal point. If the original number is greater than 1, then the decimal place is moved to the left and the exponent in the ×10 indicates how many times the number needs to be multiplied by 10.98000=9.8×10×10×10×10=9.8×104