CHE 100 - Ch. 13

156 g C12H22O11 (sucrose) is dissolved into 4.0 L of solution. What is the molar concentration of the solution? Report your answer with the correct number of significant figures.

0.11 M Molarity (M) is calculated by dividing moles (mols) of solute by Liters (L) of solution. M=moles of solute/volume of solution (L) First, you need to calculate the number of moles using the given mass and dividing by the molar mass of the substance. 156 g/342.2 g/mol=0.456 mol Then, you can solve for molarity using the molarity equation. M=0.456 mol/4.0 L=0.11M

______________ do NOT form a solution.

water and olive oil Water and oil are immiscible due to the large difference in their polarities.

A bottle of soda contains 39 grams of sucrose (C12H22O11) and 300 grams of water (H2O). What is the percent mass of sucrose in this soda?

11.5% First. you must calculate the total mass of the soda by adding the mass of sucrose (C12H22O11) and the mass of water (H2O). Total Mass=300 g+39 g=339 g Then, you find the mass percentage of sucrose (C12H22O11) by dividing its mass by the total mass calculated in step 1, and multiplying by 100. Mass% C12H22O11=39 g339 g×100=11.5% C12H22O11

What type of change is dissociation?

Physical The process of dissociation is a physical change. The compound is physically separated into its component ions.

Covalent electrolytes are typically:

depends on the substance Covalent electrolytes can be strong or weak, depending on the strength of the acid or base. Strong acids and bases are typically strong electrolytes. Nonelectrolytes do not dissociate into ions in solution; nonelectrolyte solutions do not, therefore, conduct electricity.

An electrolyte will yield ions by undergoing a:

depends on the substance Some electrolytes are ionic solids that dissociate, which would be a physical change, and some are covalent compounds that participate in a chemical reaction with solvent molecules to generate ions.

Upon the dissociation of potassium chloride, the potassium ions will interact with:

the negative end of water's dipole Because potassium ions are positively charged, they will exclusively interact with the negative end of water's dipole, since opposite charges attract.

Considering the steps involved in dissolution, which of the following do you expect to speed up a dissolution process?

- Stirring the solution vigorously - Grinding the solute down into tiny particles - Gently heating the solution A dissolution will proceed more readily when heated. Breaking up the solute as much as possible will aid in overcoming the solute-solute interactions, as will stirring the solution.

Which of the following are true of ionic electrolytes?

- They must be ionic compounds. - They yield ions in solution by strong ion-dipole interactions. Ionic electrolytes must be ionic compounds. They yield ions when ion-dipole attraction is amplified and strong interionic forces are reduced.

Of the following, which are characteristics of weak electrolytes?

- They produce a low concentration of ions when dissolved in water. - They are soluble in water. - They exhibit low conductivity. Weak electrolytes exhibit low (but still some) conductivity and produce a low concentration of ions when dissolved in water. Being able to dissolve in water means that the electrolyte is indeed soluble. Weak electrolytes are still able to generate some electric current. Nonelectrolytes do not generate any electric current.

If a compound undergoes a chemical reaction and the reaction is essentially 100% complete, the compound could have been a: (select all that apply)

- strong acid - strong base Strong acids and bases react more completely and result in strong electrolytes, while weak acids and bases do not react as completely and result in weak electrolytes.

A teaspoon of table sugar contains about 0.01 mol sucrose. What is the molarity of sucrose if a teaspoon of sugar has been dissolved in a cup of tea with a volume of 200 mL?

0.05 M Molarity (M) is calculated by dividing the number of moles (mol) of a solute by the liters (L) of a solution. The volume must be expressed in Liters. Volume expressed in milliliters (mL) must be converted to L by dividing the mL volume by 1000. M = mol solute / L solution = (0.01 mol) / (200 mL×1L/1000 mL) = 0.05

A teaspoon of table sugar contains about 0.01 mol sucrose. What is the molarity of sucrose if a teaspoon of sugar has been dissolved in a cup of tea with a volume of 200 mL?

0.05 M The concentration or Molarity (M) of a solution is calculated by dividng the moles (mol) of solute by the volume in Liters (L) of the solution as shown in the following eqaution: M=mol solute/L solution (0.01 mol)/(200 mL×1L/1000 mL)=0.05 M Note that all volumes in Molarity calculations must be converted to L if they are in any other volume units. Typically you will convert mL into L by dividing the mL volume by 1000.

Refer to the precipitation reaction below. CaCl2(aq)+2AgNO3(aq)→Ca(NO3)2(aq)+2AgCl(s) How much 1.5MCaCl2, in liters, will completely precipitate the Ag+ in 1.0Lof0.20MAgNO3 solution? Round to two significant figures. Do not include units in your answer.

0.067 L Begin with the given amount of AgNO3 solution, and use the molarity to find the number of moles of AgNO3. 1.0LAgNO3 × (0.20molAgNO3)/(LAgNO3 solution) = 0.20molAgNO3 Calculate the number of moles of CaCl2. 0.20molAgNO3 × (1molCaCl2)/(2molAgNO3) = 0.10molCaCl2 Use the molarity of CaCl2 to calculate the required volume. 0.10molCaCl2 × (LCaCl2)/(1.5molCaCl2) = 0.06666LCaCl2solution Rounding to two significant figures, the volume of CaCl2 solution is about 0.067L.

15 g NiO is dissolved into enough water to make 800. mL of solution. What is the molar concentration of the solution? Report your answer with the correct number of significant figures.

0.25 M Molarity (M) is calculated by dividing moles (mols) of solute by liters (L) of solution. M=moles of solute/volume of solution (L) First, you need to calculate the number of moles using the given mass and dividing by the molar mass of the substance. 15 g/74.692 g/mol≈0.20 mol The volume must be converted from mL to L. This is done by dividing the given mL by 1000. Then, you can solve for molarity using the molarity equation. The answer should be reported to two significant figures. M=0.20 mol/0.800 L=0.25 M

Refer to the precipitation reaction below. 3CaCl2(aq)+2Na3PO4(aq)→6NaCl(aq)+Ca3(PO4)2(s) How many liters of 0.20MCaCl2 will completely precipitate the Ca2+ in 0.50Lof0.20MNa3PO4 solution? .7Round to two significant figures. Do not include units in your answer.

0.75 L Begin with the given amount of Na3PO4 solution, and use the molarity to find the number of moles of Na3PO4. 0.50LNa3PO4solution × (0.20molNa3PO4)/(LNa3PO4) = 0.10molNa3PO4 Use the ratios in the balanced equation to calculate the number of moles of CaCl2. 0.10molNa3PO4 × (3molCaCl2)/(2molNa3PO4) = 0.15molCaCl2 Use the molarity of CaCl2 to calculate the required volume. 0.15molCaCl2 × (LCaCl2solution)/(0.20molCaCl2) = 0.75LCaCl2

Refer to the precipitation reaction below. 3BaCl2(aq)+Al2(SO4)3(aq)→2AlCl3(aq)+3BaSO4(s) How much 0.50MBaCl2 solution, in liters, will completely precipitate the Ba2+ in 1.0Lof0.15molAl2(SO4)3 solution? Round to two significant figures. Do not include units in your answer.

0.9 L Begin with the given amount of Al2(SO4)3 solution, and use the molarity to find the number of moles of Al2(SO4)3. 1.0LAl2(SO4)3 × (0.15molAl2(SO4) L)/(Al2(SO4)3) = 0.15molAl2(SO4)3 Use the ratios in the balanced equation to calculate the number of moles of BaCl2. 0.15molAl2(SO4)3 × (3molBaCl2)/(molAl2(SO4)3) = 0.45molBaCl2 Use the molarity of BaCl2 to calculate the required volume. 0.45molBaCl2 × (LBaCl2)/(0.50molBaCl2) = 0.90LBaCl2 solution

Consider the following precipitation reaction: ZnSO4(aq)+BaCl2(aq)→ZnCl2(aq)+BaSO4(s) What volume of 0.30M ZnSO4 will precipitate all the Ba2+ ions from 1.8L of 0.15MBaCl2? Round the answer to two significant figures.

0.90 L Begin with the given amount of BaCl2 solution and use the molarity to calculate the number of moles of BaCl2. 1.8 L BaCl2 solution × (0.15 mol BaCl2)/(1L BaCl2 solution) = 0.27 mol BaCl2 Then use the stoichiometry from the precipitation reaction to calculate the number of moles of ZnSO4. 0.27 mol BaCl2 × (1 mol ZnSO4)/(mol BaCl2) = 0.27 mol ZnSO4 Finally, use the molarity of the ZnSO4 solution to calculate the required volume. 0.27 mol ZnSO4 × (1L ZnSO4 solution)/(0.3 mol ZnSO4) = 0.90 L ZnSO4 solution

How many milliliters of a 0.300M calcium chloride solution is required to prepare 650.0mL of 0.0500M solution? Your answer should have three significant figures.

108 mL Use the dilution equation to solve for the volume of stock solution that is needed. C1V1=C2V2 We are given that C1=0.300M, C2=0.0500M, and V2=650.0mL. Rearrange the equation above for V1 and substitute the given values into the equation to solve for the volume of stock solution that is needed. V1=C2*V2/C1 V1=0.0500M×650.0mL/0.300M V1=108.333mL Therefore, after rounding to three significant figures, we find that the volume of stock solution that is needed is 108mL.

What is the concentration (in milligrams per milliliter) of a solution of KH2PO4 if 250mL of it can be used to prepare 1.0L of a 0.50mg/mLsolution? Your answer should have two significant figures.

2 mg/mL Given, c2=0.50mg/mL V1=250mL V2=1.0L=1000mL c1=? Use the equation c1V1=c2V2. Substituting gives c1×250mL=0.50mg/mL×1000mL. Then, c1=(0.50mg/mL×1000mL)250mL=2.0mg/mL.

If 110. grams of potassium carbonate (K2CO3) is dissolved into 300. mL of solution, what is the molarity of the solution?

2.65 M Molarity (M) is calculated by dividing moles (mols) of solute by liters (L) of solution. M=moles of solute/volume of solution (L) First, you need to calculate the number of moles using the given mass and dividing it by its molar mass. 110 g/138.204 g/mol≈0.7959 mol The volume must be converted from mL to L. This is done by dividing the given mL by 1000. Then, you can solve for molarity by dividing the calculated mols by the L of solution using the molarity equation. M=0.7959 mol/0.300 L=2.653 M The answer should have three significant figures, so round to 2.65 M.

What is the percent mass of potassium chloride in a solution made by adding 25 g of potassium chloride to 70.0 ml of water? Your answer should have two significant figures.

26% $26\text{%}$ The density of water is 1gmL, so 70.0 mL of water is equal to 70.0 g of water. Write the equation for the mass percent of solute in the solution. mass percentage=mass solutemass solution×100% Add the mass of solute, potassium chloride, to the mass of water to calculate the total mass of the solution. mass solution=25 g+70.0 g=95 g Now, substitute the mass of solute and the total mass of the solution into the original equation to calculate the mass percent of potassium chloride. mass percentage=25 g95 g×100%=26.3% Therefore, after rounding to two significant figures, we find that the mass percent of potassium chloride is approximately equal to 26%.

A stock solution of magnesium chloride has a concentration of 120 mg/mL. How many milliliters of the stock solution are required to prepare 1.5 L of 25 mg/mL solution? Your answer should have two significant figures.

310 mL Use the equation c1V1=c2V2 with c1=120 mg/mL, c2=25 mg/mL, and V2=1.5 L and solve for V1. V1=(c2*V2)/c1=(25×1.5)/120=0.3125 Therefore, 0.3125 L of the stock solution are required. Converting to mL and rounding to two significant figures gives 310 mL.

A solution has a total mass of 450 g and contains 18g of sodium nitrate (NaNO3). What is the mass percent of sodium nitrate (NaNO3) in this solution? Your answer should have two significant figures.

4% Mass Percentage is calculated by dividig the mass of the solute (NaNO3) by the total mass of the solution, and then multiplying by 100. mass percentage=mass solute/mass solution×100% mass percentage=18 g/450 g×100%=4.0%

How many milliliters of a 0.80mM ammonium hydroxide solution are required to create 2.0L of 0.30mM solution? Do not include units in the answer. Your answer should have two significant figures.

750 mL Given, M1=0.80mM M2=0.30mM V2=2.0L V1=? Use the equation M1V1=M2V2. Substituting gives 0.80mM×V1=0.30mM×2.0L. Then, V1=(0.30mM×2.0L)/0.80mM=0.75L. Converting the answer to milliliters gives 0.75L×1000mL/1L=750.mL.

Summarize these first two steps in this solution stoichiometry problem.

? First use the coefficients of the balanced equation to convert volume of one reactant to moles; then use the molarity to convert to moles of the other reactant

Why is a balanced equation like a recipe?

Because it tells you how much of each reactant you have and how much of each product you will produce.

True of false: a strong electrolyte always forms a very concentrated solution and a weak electrolyte always forms a very dilute solution.

False The terms "strong" and "weak" as they refer to electrolytes describe the extent of dissociation into ions and is not directly related to how concentrated or dilute a solution may be. A strong electrolyte is a compound that dissociates completely into ions, and a weak electrolyte is a compound that dissociates only somewhat into ions. A nonelectrolyte is a compound that can dissolve in water but does not dissociate into ions (such as sucrose).

A solution is made by adding 24.7 g of acetylcholine to 429 g of water. What is the mass percentage of acetylcholine in this solution? Your answer should have three significant figures.

First, we must calculate the total mass of the acetylcholine solution. We can do this by adding the mass of the acetylcholine and the mass of water: Total Mass=24.7g+429g=453.7g Note that the total mass is only significant to the units place, but we keep the more precise value of 453.7 for use in the rest of the calculation until we round the final result. In order to find the mass percentage of acetylcholine, we must first divide the mass of acetylcholine by the total mass of the solution, then multiply by 100%: mass percentage=mass solute/mass solution×100% =24.7g/453.7g×100% =5.441% Since the answer should have three significant figures, it is rounded to 5.44%.

Identify the option below that is characteristic of a solution.

Its components are dispersed on a molecular scale. A solution is homogenous, and its components are dispersed on a molecular scale. The physical state of a solution is generally the same as that of the solvent. Its composition, as well as the concentrations of its components, can be varied continuously within a certain range.

One way to determine the difference between a true solution and a heterogeneous mixture is by visual inspection. Many popular sports drinks have a cloudy or opaque appearance. Are these examples of solutions?

No, these are examples of heterogeneous mixtures. Solutions only scatter light minimally (similar to pure liquids) so they usually appear clear or translucent but not cloudy. Heterogeneous mixtures tend to scatter light, giving a cloudy or opaque appearance. Therefore, the cloudy sports drinks are examples of heterogeneous mixtures.

How are the coefficients in a balanced equation useful in chemistry?

The tell us the ratio of moles of each reactant needed or the theoretical ratio of moles of product produced

Which of the following is a solution?

alloy An alloy is a homogenous solid mixture of a metallic element and one or more additional a solild elements: a solid-solid solution. All of the other options lack at least one qualifying trait of a solution.

Which of the following will favor the spontaneous formation of a solution?

an increase in the disorder in the system The formation of a solution is an example of a spontaneous process: a process that, under certain conditions, occurs on its own without the requirement of energy from some external source. There are two criteria that favor, but do not guarantee, the spontaneous formation of a solution: A decrease in the internal energy of the system (an exothermic change) and an increase in the disorder in the system (which indicates an increase in the entropy of the system).

In a solution of calcium sulfide (CaS) and water, ___ is the solute.

calcium sulfide Calcium sulfide is the substance that is being dissolved into the solvent, water.

Which will conduct the most electricity?

depends on the substances It will depend on the electrolyte in question, whether ionic or covalent, as they have varying solubilities. Nonelectrolytes do not dissociate into ions in solution; nonelectrolyte solutions do not, therefore, conduct electricity.

When containers of helium and argon are connected, the gases spontaneously mix due to ___________.

diffusion The formation of solutions is a spontaneous process and occurs to increase the disorder of a system. The formation of a solution of the gases in the question will happen through diffusion.

The components of a solution:

disperse evenly For a solution to meet the criteria of being a homogenous mixture, its components must be distributed evenly about the solution so that no one area is different from another.

To conduct electricity, a substance must contain which of the following?

freely mobile charged particles For a substance to be able to conduct electricity, there must be a freely mobile charged species of some kind. This could be ions in aqueous solutions, or freely moving electrons within a solid metal wire.

At this point, after all units cancel, what will be the final unit we have just solved for?

liters

A covalent electrolyte _______.

may be a strong acid A covalent electrolyte may be a strong acid. The remaining options describe ionic electrolytes. Electrolytes are substances which, when dissolved in water, break up into cations (plus-charged ions) and anions (minus-charged ions). We say they ionize. Strong electrolytes ionize completely (100%) which is what strong acids do.

What is a possible conversion factor for converting the volume of a given substance to moles?

molarity Molarity is mol/L so you can see moles and liters (volume) in this conversion factor.

Which is NOT a solution?

mud All gases will mix homogeneously to form solutions (provided that they do not react). Alloys are homogeneous solid mixtures containing one metallic element and one or more additional solid components. Brine is a very concentrated aqueous solution of salt. Mud, on the other hand, is a suspension.

Which of the following is not an insoluble compound?

potassium chloride Compounds such as calcium carbonate (limestone), calcium phosphate (the inorganic component of bone), and iron (III) oxide (rust) are insoluble. Potassium chloride dissociates into ions in aqueous solutions

In seawater, NaCl is the ____________ and H2O is the _______________.

solute, solvent Salt is present in lesser concentrations making it the solute, while water is present in greater concentrations making it the solvent.

Dissolution occurs because:

the cations and anions will make ion-dipole interactions with the solvent When ionic compounds dissolve in water, the ions in the solid separate and disperse uniformly throughout the solution because water molecules surround and solvate the ions, reducing the strong electrostatic attractions between them. This process represents a physical change known as dissociation.