Concept explainers
In Section 2.1 it was pointed out that mass and energy are alternate aspects of a single entity called mass-energy. The relationship between these two physical quantities is Einstein’s famous equation, E = mc2, where E is energy, m is mass, and c is the
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Chemistry
- 3.83 For the reaction of nitrogen, N2, and hydrogen, H2, to form ammonia, NH3, a student is attempting to draw a particulate diagram, as shown below. Did the student draw a correct representation of the reaction? If not, what was the error the student made?arrow_forwardOn October 21, 1982, the Bureau of the Mint changed the composition of pennies (see Exercise 120). Instead of an alloy of 95% Cu and 5% Zn by mass, a core of 99.2% Zn and 0.8% Cu with a thin shell of copper was adopted. The overall composition of the new penny was 97.6% Zn and 2.4% Cu by mass. Does this account for the difference in mass among die pennies in Exercise 120? Assume the volume of the individual metals that make up each penny can be added together to give the overall volume of the penny, and assume each penny is the same size. (Density of Cu = 8.96 g/cm3; density of Zn = 7.14 g/cm3).arrow_forwardCopper atoms. (a) What is the average mass of one copper atom? (b) Students in a college computer science class once sued the college because they were asked to calculate the cost of one atom and could not do it. But you are in a chemistry course, and you can do this. (See E. Felsenthal, Wall Street Journal, May 9, 1995.) If the cost of 2.0-mm diameter copper wire (99.9995% pure] is currently 41.70 for 7.0 g, what is the cost of one copper atom?arrow_forward
- 9. When a candle has been burning for an hour, its mass is less than it was at the beginning. (a) How is it possible for the candle to lose mass without violating the law of conservation of mass? (b) How might you find the mass of the missing material? 14. Hydrochloric acid reacts with zinc. The chemical equation for this reaction is Zn(s) + 2 HCl(aq) → H2(g) + ZnCl2(aq) a) Classify this reaction. (b) Name the product that forms bubbles in this reaction. How do you know? c) How does the mass of zinc metal change as the reaction proceeds? d) What does the (aq) symbol in the equation mean? 24. Consider this chemical equation: Zn + 2 AgNO3 → Zn(NO3)2 + 2 Ag a) How many atoms of zinc are on the left side of the equation? How many are on the right? (b) How many atoms of silver are on the left side of the equation? How many are on the right? (c) Is the equation balanced? Explain. 25.How are coefficients different from subscripts in equations? 30. Consider this neutralization reaction: HCl +…arrow_forward19.78 mL of bromine contains 6.022 x 1023 bromine molecules. How many bromine atoms are in 3.00 L of bromine? (Each bromine molecule, Br2, contains two bromine atoms.)arrow_forwardBromine (atomic mass 79.904 amu) consists of 2 different naturally occurring isotopes, Br-79 (atomic mass = 78.9193 amu) and Br-81 (80.9163 amu). If a student measures out 35.47 mL of Br2(l), which has a density = 3.119 g/mL), calculate the number of atoms of Br-81 in the given volume of bromine liquid.arrow_forward
- The density of gold metal is 19.3 g/cm3, while that for silver is 10.5 g/cm3. Suppose you had the same size bar of each metal, with the dimensions 2.00 in x 10.0 cm x 760 mm. Volume of a cube is height x length x width. Which bar would have the greatest mass? Which bar contains the greater number of atoms? If the two bars were melted and mixed together to form an alloy (or mixture) what would be the total mass?arrow_forwardMatter is neither created nor destroyed in a chemical reaction. Thus, the mass of the products of a chemical reaction must be equal to the mass of the starting materials. Formally, this concept is called the law of conservation of mass. When carbon is burned in air, it reacts with oxygen to form carbon dioxide. When 16.8 g g of carbon were burned in the presence of 59.1 g of oxygen, 14.3 g of oxygen remained unreacted. What mass of carbon dioxide was produced?arrow_forwardThe mass of a copper coin is 7.83 g. Suppose it were pure copper. a) How many moles of Cu atoms would the copper contain, given that the molar mass of Cu is 63.55 g/mol? The calculation has been set up for you. You must fill in the blanks with the correct values, including units. Round your answer to 3 significant figures. 7.83 g × (y) = (z) (x) = (y) = (z) = %3D b) How many Cu atoms are present? The calculate has been set up for you. You must fill in the blanks with the correct values, including units. Round your answer to 3 significant figures and use the exponent notation for Avogadro's number (i.e. 6.022E23 atoms). Note that (z) is the same value as above, so you don't need to fill it in again below. (m) (z) × (n) (p) (m) = (n) = (p) =arrow_forward
- A college chemistry student is performing this reaction in a lab, where magnesium is burned and combines with oxygen from the air to produce magnesium oxide. The students burns 2.92 g of Mg, and there is excess oxygen from the air. They incorrectly 'culated that the mass of magnesium oxide produced was 2.42 g. Here is their work: 2.92 g 1 mol 2 mol 40.3 g = 2.42 g 1 24.3 g 1 mol 1 mol 1) What did the student do wrong? There is an error in their work. Explain specifically what part is incorrect. 2) What recommendation(s) would you give to the student regarding showing their work? There is an improvement that can be made to help them avoid this mistake in the future. pts) 3) Instead of 2.42 g, what answer should the student have gotten?arrow_forwardA student performed an experiment in Lesson 2 (the chemical reaction is shown below). The student's total measured mass of reactants was 14.87 g. Ideally, what should the mass of the products be? Explain your answer using the law of conservation of mass.arrow_forward2Mg(s) + O₂(g) → 2MgO(s) A chemistry student is performing this reaction in a lab, in which magnesium is burned and combines with oxygen from the air to produce magnesium oxide. The student burns 2.92 g of Mg with oxygen from the air. The student incorrectly calculated that the mass of magnesium oxide produced was 9.69g. The work is below: 2.92 g 1 X 1 mol 24.3 g 2 mol 1 mol X 40.3 g 1 mol = 9.69g 1) What did the student do wrong? There is an error in their work. Explain specifically what part is incorrect. 2) What recommendation(s) would you give to the student regarding showing the work? There is an improvement that can be made to help the student avoid this mistake in the future. 3) Instead of 9.69g, what answer should the student have calculated?arrow_forward
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