CHM 090 Unit 1 exam questions and answers

s orbital and p orbitals - correct answers In which orbitals would the valence electrons for carbon (C) be placed? 1.48 10-11 J - correct answers What is the nuclear binding energy of an atom that has a mass defect of 1.643 10-28 kg?Use E = mc2. (Remember: The speed of light is approximately 3.00 108 m/s.) burning a candle - correct answers A teacher wants to perform a classroom demonstration that illustrates both chemical and physical changes. Which would be the best demonstration that she could use? Temperature measures thermal energy, and heat is the flow of thermal energy. - correct answers How does heat differ from temperature? Heat is released during the process. - correct answers The enthalpy of formation of water is -285.8 kJ/mol. What can be inferred from this statement? 3.07 mol - correct answers Consider the reaction below. 2C6H14 + 19O2 12CO2 + 14H2O How many moles of hexane (C6H14) must burn to form 18.4 mol of carbon dioxide? Na2CO3 - correct answers Consider the following system at equilibrium. CaCO3(s) Ca2+(aq) + CO32-(aq) The addition of which compound will cause a shift in equilibrium because of a common ion effect? All collisions between particles are perfectly elastic. - correct answers Which postulate of the kinetic-molecular theory best describes the event in the diagram? barium - correct answers Consider the positions of barium (Ba), sulfur (S), silicon (Si), and calcium (Ca) on the periodic table. The atoms of which element require the least amount of energy to give up an electron when forming chemical bonds? Energy is transferred from faster moving molecules to slower moving molecules, and the result is the average of 15°C. - correct answers Two cups of coffee, one that is at 10°C and one that is at 20°C, are mixed. Which statement about the temperature of the mixture is correct? p block. - correct answers Elements that have complete valence electron shells are mostly found in the 0.548 J/(gi°C) - correct answers A sample of an unknown substance has a mass of 0.158 kg. If 2,510.0 J of heat is required to heat the substance from 32.0°C to 61.0°C, what is the specific heat of the substance? The rate of freezing is equal to the rate of melting. - correct answers A sample of water is taken and kept in a beaker in a freezer at a constant temperature of 0°C. If the system is at dynamic equilibrium, which of these statements is true? 22.5 kJ - correct answers A sample of propane (C3H8) has a mass of 0.47 g. The sample is burned in a bomb calorimeter that has a mass of 1.350 kg and a specific heat of 5.82 J/(g • °C). How much energy is released by the reaction if the temperature of the calorimeter rises by 2.87°C? It is a measure of the strength of the bonds between ions. - correct answers Which statement is true about crystal lattice energy? Ca and Br: Calcium easily loses electrons, and bromine gains them. - correct answers Which of the following best describes a pair of elements that will form an ionic bond? They both allow electrons to move from lower energy levels to higher energy levels. - correct answers Which statement explains how the bands in the crystal of a metal are like atomic orbitals? five - correct answers Lillian multiplies two numbers as follows: A B = C. Given that A has five significant figures and two decimal places and B has six significant figures and four decimal places, which equals the number of significant figures in C? 142.05 amu - correct answers Which is the formula mass of Na2SO4? combustion - correct answers Which type of reaction is C12H22O11 → 12C + 11H2O? phosphorus - correct answers An element has five valence electrons available for bonding. This element is most likely which of the following? 1:2 and 1:4 - correct answers Consider the balanced equation below. N2H4 + 2H2O2 N2 + 4H2O What are the mole ratios of hydrazine (N2H4) to hydrogen peroxide (H2O2) and hydrazine to water? 64.0 - correct answers The chemical equation below shows the burning of magnesium (Mg) with oxygen (O2) to form magnesium oxide (MgO).2Mg + O2 2MgOThe molar mass of O2 is 32.0 g/mol. What mass, in grams, of O2 is required to react completely with 4.00 mol of Mg? mass because it is an extensive property - correct answers Two students are given different samples of a substance and are instructed to determine the properties of the substance.Which statement describes a property that will be the same for both students? electromagnetic energy - correct answers A solar panel combines multiple photovoltaic cells. Which type of energy is used to power a solar panel? 6.15 - correct answers The chemical equation below shows the combustion of methane (CH4). CH4 + 2O2 CO2 + 2H2O The molar mass of oxygen gas (O2) is 32.00 g/mol. The molar mass of carbon dioxide (CO2) is 44.01 g/mol. What mass of CO2, in grams, will form when 8.94 g O2 completely react? The direction of the chemical equilibrium will shift to the right, favoring the forward reaction. - correct answers Consider the chemical reaction in equilibrium. H2 + I2 + heat 2HI What will happen to the chemical equilibrium if the temperature of the system is increased? 4, 3, 2 - correct answers Consider the unbalanced equation for the oxidation of aluminum._Al + _O2 _Al2O3Which sequence of coefficients should be placed in the blanks to balance this equation? calcium - correct answers A single atom of an element has 21 neutrons, 20 electrons, and 20 protons. Which element is it? It is made up of ions that are held together by ionic bonds. - correct answers Sodium chloride is made up of clear, colorless crystals. A solution of sodium chloride in water is a good conductor of electricity. Which statement describes sodium chloride?