Chem Lab 1LA Final Studyguide

A sample of nickel sulfate was found to contain 45% water by mass. What is the formula of the hydrate?

a. NiSO3 * H2O

b. NiSO3 * 3H2O

c. NiSO3* 6H2O

d. NiSO4 * 3H2O

e. NiSO4 * 7H2O

e. NiSO4 * 7H2O

Nickel sulfate is equal to NiSO4 in terms of chemical formula. As for the hydrate part, I had to calculate the mass percent by using 7(mass of water) / mass of Nickel sulfate + 7(mass0

Beer's Law is described by which of the following equations?

a. PV=nRT

b. A = -log(%T/100)

c. A = log (Io/I)

d. A = (Sigma)bC

e. M1V1 = M2V2

d. A = (Sigma)bC

A = absorbance

Sigma = molar absorptivity

b = length of light path

C = concentration

Of the following lines in the emission spectrum of helium, which corresponds to the highest energy electron transition?

a. 707 nm

b. 668 nm

c. 471 nm

d. 501 nm

e. 588 nm

c. 471 nm

energy and wavelength have an inverse relationship so a small wavelength means big energy

The process by which a hydrate compound loses water to the atmosphere is called

a. deliquescence

b. desiccance

c. hydration

d. efflorescence

e. emission

d. efflorescence

Understanding different processes

A certain solid has a density of 8.0 g/cm^3. If 4.0 of this solid are poured into 4.00 mL of water, which graduated cylinder below most closely represents the volume of water after the solid is added.

a. cylinder (a)

b. cylinder (b)

c. cylinder (c)

d. cylinder (d)

e. none of the cylinders

b. Cylinder (b)

Calculate the volume of the solid by using V = M/D. This gives you .5 and then you will add that to the 4.00 mL of water that already exists. This gives you 4.5 mL which is close to

cylinder (b)

What volume of 0.300 MCu2+ standard is required to prepare 20.00 mL of 0.160 MCu2+ solution?

a. 1.07 x 10^-2 L

b. 26.7 mL

c. 37.5 mL

d. 2.40 x 10^-2

e. 0.96 mL

c. 37.5 mL

Need to use the formula M1V1 = M2V2

so you do .3 x 20 = .16x and solve to get 37.5

Which of the following molecules is polar (has a net dipole moment)?

a. BeCl2

b. KrF2

c. SiBr4

d. CO2

e. SF2

e. SF2

Fluorine has a electronegativity of 4.0 and Sulfur has an electronegativity of 2.58. The difference is 1.42 and their geometry allows this to be polar.

In a density measurement, a liquid was delivered from a 50-mL buret. The initial volume level of the liquid is shown in figure 8a and the final volume level is shown in Figure 8b. Which number below represents the most accurate estimate of the total volume of liquid that was delivered?

a. 22.2 mL

b. 23.5 mL

c. 1.3 mL

d. 22.22 mL

e. 22 mL

a. 22.2 mL

You have to look at the figures and estimate where each of them are at. Make sure to measure accurately.

The following questions pertains to compounds that have the molecular formula C2H2CL2.

The compound(s) that is (are) nonpolar is (are)

a. x and z

b. z only

c. x and y

d. x only

e. y only

a. x and z

According to the Rydberg equation, visible light with the longest wavelength will be emitted from the hydrogen atom when an electron undergoes which of the following transitions?

a. n = 3 -> n = 2

b. n = 4 -> n = 2

c. n = 5 -> n = 2

d. n = 6 -> n = 2

e. none of the above

a. n = 3 -> n = 2

Inverse relationship

Dr. Ava Gadro weighed a sample of washing soda (Na2CO3 * nH2O) in a dry, covered crucible, for a total mass of 27.700 g. She has earlier found that the empty crucible and its cover weighed 23.930 g. She heated the crucible and its contents until all the water of hydration was driven off. Upon cooling, the sample plus crucible and cover weighed 25.326 g. How many moles of water were lost upon heating the washing soda to dryness? (molar mass Na2CO2 = 105.99 g/mol)

a. 1.000 mol

b. 0.02240 mol

c. 0.1318 mol

d. 0.07749 mol

e. 0.2093 mol

d. 0.07749 mol

Find the amount of water that was lost through simple subtraction of the certain parts. Convert the amount in grams to mols by dividing the water by it's molar mass.

Water molar mass = 18.02

From the information in Question 11, determine the molecular formula for washing soda.

a. Na2CO3

b. Na2CO3 * H2O

c. Na2CO3 * 2H2O

d. Na2CO3 * 6H2O

e. Na2CO3 * 10H2O

...

An empty flask has a mass of 50.01 g. When the flask is completely filled with pure water at 20C (density = 0.9982 g/mL), the combined mass is 255.52 g. How many mL of mercury (density = 13.534 g/mL) will the flask hold at 20C?

a. 256.0

b. 3.700

c. 16.45

d. 15.18

e. 205.9

e. 205.9

Find the density of the flask and that is the answer

D=M/V

Each of the members in the following calculation represents a quantity measured by a student in the laboratory

P = (0.100 x 0.08206 x 298.15)/1.0068

After performing the calculations, the student's calculator appeared as shown below: To the correct number of significant figures, what is the value of P?

a. 2

b. 2.43

c. 2.430

d. 2.4301

e. 2.430094

b. 2.43

The least amount of sig figs in any number in the equation is 3. option b has 3 sig figs because the two zeroes at the end are trailing 0's and count towards sig figs.

In experiment 2, you prepared a graph of 1/x vs. 1/n^2x. This graph was used to

a. determine the wavelengths of the lines in the hydrogen spectrum

b. calibrate the scale of the spectroscope

c. determine the electronic transitions corresponding to the visible spectrum of helium.

d. calculate the Rydberg constant Rh

e. none of the above

a. It showed the known and the scale

The octet rule is violated by at least one atom in each of the following species except

a. ICl2-

b. CH4

c. ClF3

d. SF4

e. BF4-

b. CH4

A student determines the density of a chunk of metal to be 5.1 g/cm^3. She then repeats the measurements four more times on the same chunk of metal and obtains values of 5.0, 4.9, 5.4, and 5.2 g/cm^3 for the density. What is the standard deviation of the five measurements?

a. 0.148

b. 0.19

c. 0.22

d. 0.17

e. 0.037

b. 0.19

Use the standard deviation formula

s=sqrt[(sum of x-mean)^2)/(n-1)]

Using the Rydberg equation, calculate the ionization energy for the hydrogen atom.

a. 1.10 x 10^-15 J

b. 2.19 x 10^-18

c. 1.10 x 10^15

d. 5.89 x 10^24

e. 1.10 x 10^-18

b. (?) 2.19 x 10^-18

A calibration curve (absorbance vs. molar concentration) prepared from standard Cu2- solution has a slope of 129.47 and a y-intercept of -0.0108. A one-cent coin weighing 2.419 g is dissolved in nitric acid to produce a Cu2+ solution with a volume of 250mL. The solution has an absorbance of 0.0523 when measured at the same wavelength and in the same cell as for the calibration curve. What is the concentration of the Cu^2+ solution?

a. 4.12 x 10^-3 M

b. 1.48 x 10^-2 M

c. 0.271 M

d. 6.76 x 10^-3 M

e. 3.96 x 10^-3 M

What is the copper content of the coin described in Question 19?

a. 2.60 percent

b. 4.44 percent

c. 2.71 percent

d. 43.3 percent

e. 9.72 percent

..

The ball-and-stick molecular model shown below is a representation of an amino acid (unshaded spheres = H). Only the connections between atoms are shown; multiple bonds and nonbonded electrons are not indicated. In order to complete the electron-dot structure of the amino acid, all the following are needed except

a. 1 nonbonded pair of electrons on the nitrogen

b. 2 nonbonded pairs of electrons on the oxygen atom labeled O2

c. 1 additional bond on the oxygen atom labeled O2

d. 1 additional bond and 1 nonbonded pair of electrons on the oxygen atom labeled O2.

e. 2 nonbonded pairs of electrons on the oxygen atom labeled O2.

...

The mass of an empty flask plus stopper is 54.232 g. When the flask is completely filled with water the new mass is 153.617 g. The flask is emptied and dried, and a piece of metal is added. The mass of the flask, stopper, and metal is 143.557. Next, water is added to the flask containing the metal and the mass is found to be 226.196. What is the density of the metal? Assume the density of water is 1.000 g/mL.

a. 0.601 g/mL

b. 10.27 g/mL

c. 5.33 g/mL

d. 1.08 g/mL

e. 0.899 g/mL

c. 5.33 g/mL

Find the mass of the metal

Find the mass of the water

Find the mass of the water the second time after everything is in the flask

Subtract the second mass from first mass = volume of metal

Divide the mass of metal by the volume of metal

If a solution has an absorbance maximum at 430 nm, what would be the perceived color of light transmitted through the solution?

a. violet

b. deep blue

c. orange

d. light blue

e. yellow

e. yellow

The formal charges on Cl and O in the structure shown for the ClO- ions are respectively

a. -2 and 1

b. -1 and 0

c. 1 and -2

d. 0 and -1

e. none of the above

d. 0 and -1

Use the formal charge formula

FC = Number of valence electrons - nonbinding valence electrons - (bonded electrons / 2)

In the chromatogram below, component N has a Rf value of approximately

a. 0.52

b. 0.17

c. 0.09

d. 0.56

e. 1.93

Use Rf formula = distance travelled by solute / distance travelled by solvent