Unit 4: Toxins

1. Reactants are the substances that are present before a chemical reaction, and products are the substances that are formed during the reaction.

3. Possible answer: Toxic substances cause harm to living organisms.

5. 1. Solid mercury chloride is added to a solution of EDTA to produce a solution containing a compound of mercury with EDTA and hydrochloric acid.

   2. If the two reactants are mixed, the solid will disappear and a mixture of two liquids remains.

1. Possible answer: When sugar melts, it changes from the solid phase to the liquid phase. When sugar dissolves in water, the sugar molecules spread throughout the water.

3. 1. The solid magnesium will react and disappear into an aqueous compound, and gas bubbles will appear.

   2. Gas bubbles will appear in the solution.

   3. A solid will form when the two solutions are mixed.

5. In both cases, the mixture of two clear solutions produces gas bubbling out of the resulting solution.

1. During a physical change, substances change form but new chemical substances are not made. During a chemical change, chemical substances are changed into other chemical substances.

3. In each case, the material changes its appearance or breaks apart, but it does not change identity. Examples include melting ice, breaking glass, grinding pepper, dissolving sugar, and bending metal.

5. 1: chemical change; 2: physical change; 3: chemical change; 4: chemical change; 5: physical change; 6: chemical change; 7: chemical change

1. Possible answer: The law of conservation of mass states that matter is not created or destroyed during a chemical reaction. The atoms involved in the reaction are rearranged but are not created or destroyed.

1. Possible answer: You need to balance chemical equations to show how many molecules, atoms, or formula units of each substance take part in the reaction or are produced by the reaction.

1. Combination reactions and decomposition reactions are opposites because combination reactions put two or more atoms or compounds together to make a new compound, while decomposition reactions break a compound into two or more atoms or compounds.

3. 1. double exchange reaction

      NaOH(aq) + HNO₃(aq) → NaNO₃(aq) 1 H₂O(l)

   2. combination reaction

      C₂H₄(g) + Cl₂(g) → C₂H₄Cl₂(g)

   3. single exchange reaction

      Cl₂(g) + MgBr₂(s) → Br₂(s) + MgCl₂(s)

5. SO₃(g) + H₂O(l) → H₂SO₄(aq)

1. Possible answer: Identifying physical or chemical changes through observations alone is difficult because often no change occurs that can be detected by sight or smell.

3. 1. Each reactant has ionic bonds because they both consist of metal atoms bonded to nonmetal atoms or polyatomic ions.

   2. double exchange reaction c. chemical change

   3. A balanced reaction shows that matter is conserved because all of the atoms in the reactants are accounted for in the products.

   4. calcium phosphate

1. Possible answer: Toxicities of most substances are measured by exposing laboratory animals to the substance in different dosages.

5. 1. 90,600 mg

   2. 227,000 tablets

1. Possible answer: If you know the mass of an individual object in a large group of objects with the same mass, you can use it and the total mass to calculate the total number of objects.

5. 740 marbles will have a greater mass than 740 tiny plastic beads because the mass of a single marble is greater than the mass of a single bead.

7. 333 g of red jelly beans

9. 0.000000000000000000000327 g

1. The average atomic mass of atoms of an element is given on the periodic table in units of amu.

5. 1. 1 mol carbon

   2. 1 mol iron

   3. 1 mol gold

   4. 1 mol gold

1. To determine the molar mass of sodium chloride, add the atomic mass of sodium and the atomic mass of chlorine to determine the mass of one unit of sodium chloride. The atomic mass in amu is the same as the molar mass in moles.

3. Ne(g): 20.2 g/mol, Ca(s): 40.1 g/mol, CO₂(g): 44.0 g/mol, CaCO₃(s): 100.1 g/mol, CH₄O(l): 32.0 g/mol, C₂H₆O(l): 46.1 g/mol, Fe₂O₃(s): 159.7 g/mol

5. 1. 10.0 g calcium, Ca

   2. 5.0 g sodium fluoride, NaF

   3. 2.0 g iron oxide, FeO

1. To convert between moles of a substance and grams of the substance, use the formula: mass (g) = molar mass · moles.

3. 12.0 mol

5. 169 g BaO₂

7. 1. 1.0 mol Cu₂O(s)

   2. 1.0 mol Cu₂O(s)

   3. Cu₂O(s) represents the best deal for the company because you get twice as much copper for the same price.

1. Possible answer: A comparison of the amount of each compound needed to make a soft drink taste sweet provides evidence that aspartame is sweeter than fructose. It takes many more molecules of fructose than aspartame to sweeten the drink.

3. 1. about 360 cans

   2. 0.00072 mol/kg

3. Possible answer: Scientific notation is a useful tool for chemists because it is often necessary to use very large or very small numbers in calculations. Scientific notation simplifies these calculations and also makes comparison of the values easier.

5. AgCl, NaCl, LiCl

1. Possible answer: “Uniform throughout” means that the components of the solution are so well mixed that two samples taken from anywhere in the solution will be identical.

5. In order of increasing molarity, the solutions are c, a, b.

7. In order of increasing molarity, the solutions are a, 0.56 M, c, 0.58 M, and b, 1.1 M.

1. Concentration refers to the amount of a substance divided by the volume in which the substance is dissolved. Two solutions of different volumes can have the same concentration if the proportion of the substance to the volume is the same.

5. a. The first two solutions have the same number of molecules. Each of these solutions has more molecules than the third solution. The number of molecules in each sample is the product of the molarity and the volume. The first two solutions have 1 mol of molecules, and the third solution has 0.5 mol of molecules. b. All three solutions have the same concentration, 1.0 M. Molarity is a measure of concentration. c. The 1.0 L sucrose solution has the greatest mass because each sucrose molecule has more mass than each glucose molecule. Therefore, one mole of sucrose has more mass than one mole of glucose. Also, one mole of sucrose has more mass than half a mole of sucrose.

9. 1. 0.25 L

   2. 1.5 L

   3. 6.0 L

   4. 300 L

1. Possible answer: To prepare a 0.25 molar solution of sugar, you would calculate the mass of 0.25 mol of sugar, then measure the amount of sugar and dissolve it in enough water to make 1 L of solution.

3. 1. 29 g

   2. 220 g

   3. 60 g

5. 1. 10 L

   2. 0.33

   3. 0.18 L

7. 1.0-liter solution with 20 g of glucose

1. A substance dissolved in the water adds mass to the solution. A sample of contaminated water should have a greater density than a sample of pure water. If this difference can be measured, the greater density indicates that the water is not pure.

3. The 0.10 M copper chloride (CuCl₂) solution has a greater density than the 0.10 M potassium chloride (KCl) solution. Copper chloride has a molar mass of 134.5 g and potassium chloride has a molar mass of 75.6 g. So if you have equal volumes of each solution there would be more mass in the copper chloride solution. And if the mass is greater, the density is greater.

7. The sodium bromide (NaBr) solution would weigh the most because it has more solute added than the sodium hydroxide (NaOH) solution. The KCl weighs about half as much as the other two samples because a 500 mL aqueous solution will always weigh less than a 1 L aqueous solution.

1. Possible answer: Knowing exactly how many moles or grams of contaminant are in a water sample determines whether the sample is toxic because toxicity is based on dosage.

3. 1. 0.00002 mol Pb²⁺

   2. 0.0066 g Pb (NO₃)₂

   3. 0.0041 g Pb²⁺

1. Possible answer: Acids have a sour taste and they can burn the skin in concentrated form. Bases have a bitter taste and a slippery feel. Bases can also cause skin burns in concentrated form. Most acidic and basic solutions are colorless and odorless.

1. According to the Arrhenius theory, an acid is a molecule that dissociates to form hydrogen ions in solution and a base is a substance that dissociates to form hydroxide ions in solution.

7. Washing soda, Na₂CO₃, forms a basic solution because it accepts a proton from water, thereby forming a hydroxide ion in solution.

1. The pH of a solution is equal to the negative logarithm of the H⁺ concentration. Therefore, the pH increases by 1 as the hydrogen ion concentration decreases by a factor of 10.

7. pH = –0.40

1. When you add water to an acidic solution, the pH of the solution increases to a maximum of 7.

5. Because the concentration of hydrogen ions contributed by the acid is less than the concentration of hydrogen ions in pure water, the addition of 1 × 10^–9 moles of HCl does not affect the pH of pure water.

7. 1. 0.075 mol

   2. 0.068 M

   3. pH = 1.2

1. Two ways to make a strong acid solution safer are dilution with water and neutralization with a base.

5. Each mole of sulfuric acid forms two moles of hydrogen ions in solution, while each mole of sodium hydroxide forms one mole of hydroxide ions. Therefore, the final solution has more hydrogen ions than hydroxide ions, so it is acidic and the pH is less than 7.

3. 1000 mL

5. 1. The final solution is acidic because the solution has more H⁺ ions than OH^– ions.

   2. The final solution is neutral because the solution has equal numbers of H⁺ ions and OH^– ions.

   3. The final solution is basic because the solution has fewer H⁺ ions than OH^– ions.

1. According to the Arrhenius theory, an acid is a substance that dissociates to form hydrogen ions in solution and a base is a substance that dissociates to form hydroxide ions in solution. According to the Brønsted-Lowry theory, an acid is a substance that donates protons in solution while a base is a substance that accepts protons. This is similar to the Arrhenius theory, but it accounts for bases that do not dissociate to form hydroxide ions.

5. 1. Sodium bicarbonate can be classified as a base because it accepts a proton from water, forming hydroxide ions.

   2. Sodium bicarbonate was available in case sulfuric acid spilled. The sodium bicarbonate could have been used to neutralize any acid that was spilled.

1. A precipitate is an insoluble compound that forms as a product of a chemical reaction in solution.

3. Possible answer: A spectator ion is an ion that is present in both the reactants and the products of a chemical reaction. Spectator ions do not participate in the reaction.

1. Possible answer: Coefficients are important in chemical equations because they represent the proportion in which reactants combine to form products.

5. 1. 0.10 mol

   2. 5.8 g

1. Possible answer: You need to convert between grams and moles to use mole ratios to find the right mass proportions of reactants.

3. 1. 12.6 g

   2. 19.8 g NaCl, 47.0 g PbCl₂

5. 1. AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq)

   2. 0.037 mol AgNO₃; 0.077 mol NaCl

   3. silver nitrate, AgNO₃

   4. 5.3 g AgCl; 3.1 g NaNO₃

   5. 2.3 g NaCl

1. Possible answer:

1. 1. Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g)

   2. 2KClO₃(s) → 2KCl(s) + 3O₂(g)

   3. S₈(s) + 24F₂(g) → 8SF₆(g)

   4. 4Fe(s) + 3O₂(g) → 2Fe₂O₃(s)

3. 1. limiting reactant: HCl; 1.87 g ZnCl₂ made

   2. limiting reactant: KClO₃; 0.608 g KCl made

   3. limiting reactant: F₂; 1.28 g SF₆

   4. limiting reactant: Fe; 1.43 g Fe₂O₃

5. A neutralization reaction is a chemical reaction in which an acid and a base combine to form a salt and water.

9. 36 g