LAB EXAM 1

Select all that apply. Identify the piece(s) of glassware you will need to accurately and precisely prepare 250.00 mL of a 0.100 M NaCl solution from a 2.50 M NaCl stock solution. The stock solution is stored in a 1 L bottle.

Placing the 10 mL volumetric pipet directly into the bottle of stock solution could contaminate the stock solution; therefore, the stock solution should be first poured into a 50 mL beaker.After 10 mL of stock solution has been measured in the volumetric pipet, it should be transferred to the250 mL volumetric flask. Then water should be added to 250 mL mark and thoroughly mixed.

A student needs to determine the density of an irregularly shaped object. This student prepares a solution mixture where the object is suspended. The collected data is shown in the table below. LiquidDensity gmLVolume (mL)Chloroform1.46510.21Ethanol0.7894.33 Determine the density of the object. Object's density = g mL

1.26 g mL

Which of the following is a gas-forming reaction?

Na2CO3(aq) + HCl(aq) →

An object with a density of 1.26 g mL is placed into each of the liquids listed in the table below. Determine whether the object will float, sink, or be suspended in the liquid. Ethanol0.789 Glycerol 1.259 Mercury13.590 Water1.000

sinks, sus, floats, sinks

Which of the following is a gas-forming reaction?

Na2CO3(aq) + HNO3(aq) →?????

In which of the following does no reaction occur?

Na2SO4(aq) + KOH(aq) →

A student needs to determine the density of an irregularly shaped object. This student prepares a solution mixture where the object is suspended. The collected data is shown in the table below. LiquidDensity gmLVolume (mL)Glycerol1.2596.21Isopropanol0.8024.13 Determine the density of the object. Object's density = g mL

1.08 g mL

To determine the concentration of citric acid, you will need to titrate this solution with 0.100 M NaOH. You are given a 1.00 M NaOH stock solution and will need to make enough 0.100 M NaOH to perform 3 titrations. For each titration, you will use 50.0 mL of 0.100 M NaOH solution. (a)Calculate the total volume (in mL) of the diluted solution you will need to prepare for the 3 titrations. mL(b)Determine the minimum volume (in mL) of 1.00 M NaOH stock solution needed to prepare the 0.100 M NaOH solution. mL

a. 0.0150 moles NaOH b.15.0 mL 1.00MNaOH

Place each of the following into one of the three major classes of chemical reactions:precipitation, acid-base, or oxidation-reduction. a.Mg(s) + HCl(aq) → b.NaOH(aq) + FeCl3(aq) → c.NaCl(aq) + AgNO3(aq) → d.NaOH(aq) + HCl(aq) →

a. oxidation-reduction b.precipitate c.precipitate d.strong base

What is the net ionic equation for each of the following reactions? a. Al(s) + HCl(aq) → b. CaCl2(aq) + H2SO4(aq) →

a.2Al(s)+6H+(aq)-->2Al^3+(aq)+3H2(g) b.Ca^2+(aq)+SO4^2-(aq)-->CaSO4(s)

(a) Which of the following reactions will produce a precipitate? (b) Write the net ionic equation for the precipitation reaction in Part A. Remember to include the proper physical states and charges of ions.

a.NaOH(aq) + MgCl2(aq) → b.Mg^2+(aq)+2OH-(aq)-->Mg(OH)2(s)

(a) After measuring the mass of a solid in a weighing vessel, what are the proper steps to add the solid to a volumetric flask for making a solution? (b) What would happen to the molarity of the solution if you forgot to rinse the funnel?

a.Use a funnel through which the solid is poured into the flask, then rinse the funnel to ensure all residual solid is added to the flask. b.The molarity of the solution in the flask would be lower than the calculated value.

Given the following information, calculate the density in g/mL of an irregular solid. Mass of weighing vessel 1.005g Mass of solid + weighing vessel9.441g Volume of liquid in graduated cylinder3.45 mLVolume of liquid in graduated cylinder +volume of solid5.35 mL

Density = mass (g) volume (mL) = 8.436 g 1.90 mL = 4.44 g mL

Select all of the following reactions that produce a precipitate.

KI(aq) + Pb(NO3)2(aq) →, NaOH(aq) + FeCl3(aq) →, BaCl2(aq) + H2SO4(aq) →

A student experimentally determines the density of a metal cube using the caliper method, liquid displacement method, and suspension method. The experimentally determined densities are listed in the table. The cube's true density is 1.9822 g/cm3. Caliper1.89 Liquid Displacement1.70 Suspension2.11

Liquid Displacement < Suspension < Caliper

What are the spectator ions in the reaction between aqueous solutions of NaOH and Ni(NO3)2?

NO3−, Na+

Determine the volume (in mL) of a 0.250 M solution of hydrochloric acid needed to make 250.0 mL of a 0.0500 M hydrochloric acid solution.

0.01250 moles HCl × 1 L 0.250 moles × 1000 mL 1 L = 50.0 mL 0.250 M HCl

A solid is weighed on the balance using the following steps: 1. The balance is tared. 2. Weighing paper is placed on the balance and the mass displayed is 0.806 g 3. An object is added to the weighing paper and the mass displayed is 1.050 g What is the mass of the object?

.244 g

What mass of solid copper(II) sulfate is needed to make 500.0 mL of 0.0300 M copper(II) sulfate solution?

0.0150 moles × 159.61 g1 mole = 2.39 g

What are the spectator ions in the reaction between aqueous solutions of Na2CO3 and AgNO3?

Na+, NO3−

Part 1 out of 2 A student experimentally determines the density of a plastic cube using the caliper method, liquid displacement method, and suspension method. The cube's true density is 0.9822 g/cm3. Use the student's collected data below to answer the following questions. Student's Collected Data Cube's Mass0.66g Caliper Method Edge Length0.85 cm Liquid Displacement Method Volume of Liquid5.5 mLVolume of Liquid + Object6.2 mL Suspension Method LiquidDensity gmLLiquid VolumeObservationEthanol0.7897.5Cube suspendedin mixtureGlycerol1.2594.8 Part ADetermine the density of the cube for each method. Report each answer to the correct number of significant figures.

Caliper Method Use the data from the caliper method and determine the cube's volume.Cube's volume = (0.85 cm)3 = 0.85 cm × 0.85 cm × 0.85 cm = 0.6141 cm3 (unrounded)= 0.61 cm3 (rounded)Calculate the density. Note that extra digits were brought into this step of the calculation.Cube's density = 0.66 g0.6141 cm3 = 1.1 gcm3Recall that 1 cm3 = 1 mL, so that density is 1.1 g/mL.Liquid Displacement MethodUse the mass and change in volume from the collected data to calculate the density.Cube's density = 0.66 g(6.2 − 5.5) mL = 0.9 gmLSuspension MethodWhen the cube is suspended in a liquid, the density of the cube is equal to the density of the liquid.Use the volume of each liquid and its associated density to determine the total mass and total volume of the solution mixture.Total volume = (7.5 + 4.8) mL = 12.3 mLTotal mass = (7.5 mL × 0.789 g/mL) + (4.8 mL × 1.259 g/mL) = 11.9607 g (unrounded)= 12.0 g (rounded) Then calculate the cube's density.Cube's density = Mixture's density = 11.9607 g12.3 mL = 0.972 gmLPercent error = │experimental value − true value│true value × 100Caliper Method Percent Error = 12%Liquid Displacement Percent Error = 8%Suspension Method Percent Error = 1.0%The suspension method is most accurate.

Identify the most accurate method for measuring the volume of an irregularly shaped unknown object shown below. (nut)

If an object is irregularly shaped, its dimensions are not well-defined nor will the side have the same length. Thus, the length of its sides cannot be used to calculate the volume.Density is dependent upon the composition of a substance. If the composition or identity of the irregularly shaped object is not known, the density of the object cannot be looked up in a reference table.Because no two objects can occupy the same space, the volume of an irregularly shaped object can be determined by adding the solid to a liquid and measuring the change in volume

A student experimentally determines the density of a metal cube. The edge length of the cube is measured using calipers. The cube's true density is 12.30 g/cm3. Use the student's collected data below and calculate the percent error for the measurement. Cube's Mass65.611 gEdge Length1.72 cm

Percent error = │12.9 gcm3 − 12.30 gcm3│12.30 gcm3 × 100 = 4.80%

Identify the most appropriate method to measure the mass of a sample of white powder.

Place a weighing vessel on the balance and tare the balance. Then add the sample of white powder to the weighing vessel and record the mass.

Part 1 out of 4 A student needs to determine the density of an irregularly shaped object with a mass of 4.55 g. Part A:The student fills a 10 mL graduated cylinder with deionized water. Use the image below to determine the volume of water in the graduated cylinder. Report the answer to the correct number of significant figures. a. Initial volume of water = mL Part B: The student then adds the object to the graduated cylinder. Use the image below and determine the volume of water and the object. Report the answer to the correct number of significant figures. Volume of water + object = mL Part C: Calculate the volume of the object. Report the answer to the correct number of significant figures. Volume of the object = mL Part D: The mass of the irregularly shaped object is 4.55 g. Determine its density. Report the answer to the correct number of significant figures. Density of object = g mL

a. 2.05 b. 4.00 c. 1.95 d. 2.33

You have been asked to make 250.0 mL of a 0.180 M solution of calcium nitrate. a.Calculate the mass (in g) of solid calcium nitrate needed to make the solution. b.To accurately and precisely prepare the solution, the solid calcium nitrate should be added to a 250 mL ____. c.What are the proper steps for dissolving the calcium nitrate?

a.7.38 g calcium nitrate b.250 mL volumetric flask c. You should dissolve the solid in the flask before adding the full volume of water. To dissolve the solid, add a small amount of water to the flask and swirl.After the solid is completely dissolved in the small volume of water, add water to the fill line of the volumetric flask.cap the flask and invert the solution several times.

You observed the formation of several precipitates in the Reactions in Solution lab exercise. Identify the precipitate in each of the following reactions: a. The yellow precipitate formed in the reaction between KI and Pb(NO3)2 is . b. The white precipitate formed in the reaction between BaCl2 and H2SO4 is . c. The brown precipitate formed in the reaction between NaOH and FeCl3 is . d. The blue precipitate formed in the reaction between CuSO4 and NaOH is .

a.PbI2 b.BaSO4 c.Fe(OH)3 d. Cu(OH)2

An object with a density of 0.87 gmL is placed into each of the liquids listed in the table below. Determine whether the object will float, sink, or be suspended in the liquid.Bromine3.120 Dichloromethane 1.326 Isopropanol0.802Toluene0.867

float, float, sink