Elena makes the table below to determine the number of atoms of each element in the chemical formula 3(NH4)2SO4. A table with 3 columns and 4 rows. The first column labeled element has entries nitrogen, hydrogen, sulfur, oxygen. The second column labeled calculation has entries 1 times 2 times 3 , 4 times 2 times 3, 1 times 4 times 3, 4 times 3. The third column labeled total atoms has entries 6, 24, 12, 12. What mistake did Elena make? She should not have multiplied the sulfur atoms by the subscript 4. She should not have multiplied the nitrogen atoms by the subscript 2. She should not have multiplied the oxygen atoms by the coefficient 3. She should not have multiplied the hydrogen atoms by the coefficient 3.

Melting and boiling are endothermic processes. this means that these processes absorb energy from their surroundings in order to occur. use this information and the data you collected in the phase change gizmo to describe what happens to the temperature of water when you boil it, then explain why this result occurs.

Astudent made a graph plotting the progress of a reaction over time. the student forgot to label the y-axis of the graph. a graph is shown with two graph lines. one graph line starts at a higher position on the y axis and slopes downwards towards the right. the other graph line starts at a lower position on the y axis and slopes upwards towards the right. the two graph lines stop short of intersecting each other and continue as separate lines which gradually become straight and parallel to the x axis. a vertical line is shown at a point where the two graph lines finally became parallel to the x axis. this vertical line is labeled equilibrium. the title on the x axis is time and an arrow pointing towards the right is shown above time. the title on the y axis is left blank. what best explains the label that the student should use on the y-axis? amount, because as the amount of product decreases, the amount of reactant increases over time. reaction rate, because forward and backward reaction become equal at equilibrium. amount, because the amounts of reactants and products become constant after equilibrium is reached. reaction rate, as the rate of forward reaction increases and rate of backward reaction decreases over time.

How are evaporation and sublimation similar? a both involve the formation of a gas. b both release energy to the surroundings. c both take place throughout a solid. d both take place at the surface of a liquid.