Question 1

The density of a gas is 1.35 g/L at standard temperature and pressure (STP). What is the molar mass of the gas at STP?

Accepted Answer

A) 0)0603 g/mol 
B) 6)02 g/mol 
C) 22.4 g/mol 
D) 30.2 g/mol

Question 2

Which of the following statements best explains why water vapor condenses as temperature decreases?

Accepted Answer

A) Collisions between water vapor molecules become elastic. 
B) Water vapor molecules chemically react when they collide. 
C) Water vapor molecules are pulled together by the force of gravity. 
D) Attractive forces between water vapor molecules overcome molecular motion.

Question 3

The pH of milk is 6.4. Based on this information, which of the following statements best describes milk?

Accepted Answer

A) It is very basic. 
B) It is very acidic. 
C) It is slightly basic. 
D) It is slightly acidic.

Question 4

Four different gases are all observed to have the same temperature. Which of the following conclusions is supported by this observation?

Accepted Answer

A) All four gases must have the same mass. 
B) All four gases must have the same pressure. 
C) All four gases must have equal numbers of particles. 
D) All four gases must have equal average kinetic energies.

Question 5

Which of the following statements applies to a nuclear fission reaction?

Accepted Answer

A) The reaction has no commercial applications. 
B) The reaction takes place only at very high temperatures. 
C) The reaction produces only shortlived radioactive waste. 
D) The reaction releases large amounts of energy when nuclei split apart.

Question 6

Which of the following elements is a member of the halogen family and is located in period 3?

Accepted Answer

A) argon (Ar) 
B) bromine (Br) 
C) chlorine (Cl) 
D) sulfur (S)

Question 7

Which of the following statements explains why the bond in hydrogen chloride (HCl) is polar covalent?

Accepted Answer

A) The atomic mass of chlorine is greater than that of hydrogen. 
B) The electronegativity of chlorine is greater than that of hydrogen. 
C) The diameter of a chlorine atom is greater than that of a hydrogen atom. 
D) The number of valence electrons in a chlorine atom is greater than that in a hydrogen atom.

Question 8

Which of the following statements best explains why ice floats on water?

Accepted Answer

A) Water has a higher specific heat than ice. 
B) Ice has the same molecular mass as water. 
C) Heat is absorbed when water changes from the solid state to the liquid state 
D) Hydrogen bonding causes water to be less dense in the solid state than in the liquid state.

Question 9

Which of the following is not true of a sample of gas as it is heated in a rigid, closed container?

Accepted Answer

A) The pressure of the molecules increases. 
B) The average speed of the molecules increases. 
C) The average distance between molecules increases. 
D) The number of collisions between molecules increases.

Question 10

Which of the following statements describes all exothermic reactions?

Accepted Answer

A) Exothermic reactions form gases. 
B) Exothermic reactions require a catalyst. 
C) The energy of the reactants is lower than the energy of the products. 
D) The energy of the reactants is higher than the energy of the products.

Question 11

Which of the following pieces of evidence best supports Bohr's idea that electrons occupy specific energy levels within an atom?

Accepted Answer

A) Sodium atoms become positive ions when they lose electrons. 
B) Each element emits a unique brightline spectrum when it falls from an excited state to a ground state. 
C) Beryllium atoms bombarded with alpha particles produce beams that are not influenced by magnetic fields. 
D) Each element has physical and chemical properties that are unique to that element and different from those of other elements.

Question 12

The air inside a beach ball is at a temperature of 25°C and a pressure of 1.0 atm. If the ball contains 0.85 mol of air, what is its volume?

Accepted Answer

A) 1)7 L 
B) 6)1 L 
C) 21 L 
D) 27 L

Question 13

The pH of four different solutions of common materials is measured. Which of the following lists the solutions in order from most acidic to most basic?

Accepted Answer

A) battery acid, lemon juice, blood, laundry detergent 
B) lemon juice, battery acid, blood, laundry detergent 
C) laundry detergent, blood, lemon juice, battery acid 
D) battery acid, blood, laundry detergent, lemon juice

Question 14

Which of the following statements describes a difference between a mixture and a pure substance?

Accepted Answer

A) A mixture tends to be homogenous, while a pure substance tends to be heterogeneous. 
B) A mixture has a specific melting point, while the melting point of a pure substance can vary. 
C) The density of a mixture can change with temperature, but the density of a pure substance cannot change. 
D) The composition of a mixture can vary from sample to sample, but the composition of a pure substance is always the same.

Question 15

Atoms of element A and atoms of element B react to form a compound. In the reaction, the radius of each atom of element A is decreased. Which of the following explains this decrease in atomic radius in the reaction?

Accepted Answer

A) The atoms of element A lose electrons to atoms of element B. 
B) The atoms of element A gain neutrons from atoms of element B. 
C) Nuclear particles are converted into energy in atoms of element A. 
D) Protons become more densely packed in the nuclei of element A atoms.

Question 16

Which of the following describes the separation of the components of a mixture?

Accepted Answer

A) Water is broken down into hydrogen and oxygen. 
B) Salt is isolated from seawater through evaporation. 
C) Propane reacts with oxygen to form carbon dioxide and water. 
D) Calcium carbonate decomposes to form calcium oxide and carbon dioxide.

Question 17

Water cools from 2°C to -2°C. During this time, what happens to the motion of the molecules?

Accepted Answer

A) The motion of the molecules stops. 
B) The motion of the molecules increases. 
C) The motion of the molecules decreases. 
D) The motion of the molecules remains the same.

Question 18

Which of the following comparisons correctly describes subatomic particles?

Accepted Answer

A) An electron has a negative charge and a mass larger than the mass of a proton. 
B) A neutron has a negative charge and a mass smaller than the mass of a proton. 
C) A neutron has a neutral charge and a mass larger than the mass of an electron. 
D) A proton has a positive charge and a mass smaller than the mass of an electron.

Question 19

Which of the following statements describes properties of most metals?

Accepted Answer

A) They have high melting and boiling points. 
B) They accept electrons to form negative ions. 
C) They have densities lower than that of water. 
D) They share electrons to form covalent bonds.

Question 20

When stirred in 30°C water, 5 g of powdered potassium bromide, KBr, dissolves faster than 5 g of large crystals of potassium bromide. Which of the following best explains why the powdered KBr dissolves faster?

Accepted Answer

A) Powdered potassium bromide exposes more surface area to water molecules than large crystals of potassium bromide. 
B) Potassium ions and bromide ions in the powder are smaller than potassium ions and bromide ions in the large crystals. 
C) Fewer potassium ions and bromide ions have been separated from each other in the powder than in the crystals. 
D) Powdered potassium bromide is less dense than large crystals of potassium bromide.

Exam 2: Chemistry

The density of a gas is 1.35 g/L at standard temperature and pressure (STP) . What is the molar mass of the gas at STP?