Chemistry Praxis Exam Prep Questions And Answers 2023

Chemistry Praxis Exam Prep Questions And Answers 2023 The specific heat of liquid water is 1 cal/kg°C. The specific heat of ice is half of that, at 0.5 cal/kg°C. Compared with that for 2 kg of liquid water, how much heat is needed to change the temperature of 2 kg of ice by 10°? 1. Four times as much heat is needed to change the temperature of the ice. 2. Twice as much heat is needed to change the temperature of the ice. 3. Half as much heat is needed to change the temperature of the ice. 4. One fourth as much heat is needed to change the temperature of the ice. - ANS-3. Half as much heat is needed to change the temperature of the ice. Which of the following correctly explains the difference between heat and thermal energy in science? 1. An object has thermal energy, but heat is transferred between objects. 2. An object has heat, but thermal energy is transferred between objects. 3. There is no difference. Heat and thermal energy are the same thing. 4. Heat is a measure of how hot an object is, whereas thermal energy is a measure of how fast the object's molecules move. - ANS-1. An object has thermal energy, but heat is transferred between objects. The specific heat of oak is 0.58 cal/g°C. How much heat is required to change the temperature of 10 grams of oak by 10°C? 1. 5.8 cal 2. 580 cal 3. 0.58 cal 4. 58 cal - ANS-4. 58 cal Which of the laws of thermodynamics prohibits any process from being 100% efficient? 1. the zeroth law 2. the first law 3. the second law 4. The first and second laws when taken together prohibit 100% efficiency. - ANS-3. the second law; often called the law of entropy; prohibits 100% efficiency in any process Determine the change in internal energy of a pot of eggs put on the stove and brought to a boil if 200 kJ of heat is added to the water, 80 kJ of heat escapes from the pot, and the escaping steam does 25 kJ of work vibrating and lifting the lid of the pot. 1. 95 kJ 2. 175 kJ 3. 145 kJ 4. 305 kJ - ANS-1. 95kJ (delta U = Q - W) Which of the following will give off energy if used as fuel in a fission reaction? 1. helium (He) 2. thorium (Th) 3. beryllium (Be) 4. hydrogen (H) - ANS-2. thorium (Th) Which of the following is powered by fusion reactions? 1. currently functioning nuclear 2. power plants 3. heating of Earth's interior 4. the Sun launching rockets for satellites - ANS-3. the Sun Select from the following list all of the problems with the planetary model of the atom. 1. It did not explain why electrons do not fall into the nucleus. 2. It did not model the behavior of heavier elements. 3. It proposed that atoms are the smallest particles of matter. 4. It did not allow for the presence of neutrons in the atom. - ANS-1. It did not explain why electrons do not fall into the nucleus. 2. It did not model the behavior of heavier elements. Which of the following is the best general description of radioactivity? 1. The absorption of particles from space. 2. An exchange of particles from one atomic nucleus to another. 3. The stripping of electrons from an atom. 4. A release of energy from the nucleus of an atom. - ANS-4. A release of energy from the nucleus of an atom. Which of the following is emitted from the nucleus during alpha decay? 1. a helium nucleus 2. one or more protons 3. an electron 4. pure energy; no protons, electrons, or neutrons - ANS-1. a helium nucleus In which of the following types of bonds are electrons transferred from one atom to another? CONTINUES...