2. Which gas has the lowest density at 25 °C and 1 atm?

Select one:

a. O₂

b. Ar

c. N₂

d. F₂

e. C₃H₈

4. If the volume of a confined gas is expanded to four times the original volume while its temperature remains constant, what change will be observed?

Select one:

a. The pressure of the gas will decrease to 1/4 its original value.

b. The pressure of the gas will decrease to 1/2 its original value.

c. The pressure of the gas will remain unchanged.

d. The pressure of the gas will increase to twice its original value.

e. The pressure of the gas will increase to four times its original value.

5. 36.6 L of He gas at STP is pumped into a 10.0-L tank containing 1.0 atm of O₂ at 25 °C. What is the total pressure in a tank at 25 °C?

Select one:

a. 2.0 atm

b. 5.0 atm

c. 5.4 atm

d. 8.0 atm

e. 8.8 atm

Write the balanced complete ionic equations and net ionic equations for the reactions that occur when each of the following solutions are mixed. (Type your answers using the format [NH4]+ for NH4+ or Ca3(PO4)2 for Ca3(PO4)2. Use the lowest possible coefficients.)

(a) Cr2(SO4)3(aq) and (NH4)2CO3(aq)

complete ionic equation:
  (aq) +  CO32-(aq) +  Cr3+(aq) +  SO42-(aq)    (s) +  NH4+(aq) +   (aq)

net ionic equation:
Cr3+(aq) +   (aq)    (s)




(b) FeCl3(aq) and Ag2SO4(aq)

complete ionic equation:
  (aq) +  Cl-(aq) +  Ag+(aq) +  SO42-(aq)    (s) +  Fe3+(aq) +   (aq)

net ionic equation:
Ag+(aq) +   (aq)    (s)




(c) Al2(SO4)3(aq) and K3PO4(aq)

complete ionic equation:
  (aq) +  PO43-(aq) +  Al3+(aq) +  SO42-(aq)    (s) +  K+(aq) +   (aq)

net ionic equation:
Al3+(aq) +   (aq)    (s)

FAST ANSWER PLEASE FOR BUFFER SOLUTION QUESTION. Would appreciate full working out thanks.

Solution C is made by mixing 55.6 mL of 0.16 M ammonium chloride (NH₄Cl) with 60.3 mL of 0.26 M ammonia solution.

pKa(NH4+) = 9.24

a) Calculate the pH of Solution C.

b) Calculate the pH of the buffer Solution C if 0.14 g of NaOH (molar mass = 40.0 g/mol) is added (assuming no change in volume).

Which reactant, and how much of it, remains after the reaction of 40.0g of V₂O₅ (FW=181.9g/mol) with 40.0g of calicuim based on the following chemical equation?

V₂O₅ + 5Ca----> 2V+5CaO

Possible Answers

0.810g Ca

3.6g Ca

.801g V₂O₅

3.6g V₂O₅

4.52g V₂O₅

1. The following question deals with nickel(II) nitrate hexahydrate.

   1. a) What is the molecular formula for nickel(II) nitrate hexahydrate?

   2. b) What is the molar mass of nickel(II) nitrate hexahydrate?

   3. c) What is the concentration of a nickel(II) nitrate stock solution when 114.2 g of nickel(II) nitrate hexahydrate is dissolved to a final volume of 250.0 mL?

   4. d) What is the concentration of a dilute nickel(II) nitrate solution after 1.55 mL of the above stock solution is diluted to a final volume of 25.0 mL?

A student dissolved 5.05 g of KNO3 in 100.302 g of water. The temperature changed from 25 to 21.7°C. Calculate the enthalpy of solution the student experimentally found in kJ/mole of KNO3. Is this an endothermic or an exothermic
reaction?

Calculate the equilibrium concentration of [FeSCN2+] in Part A if 10.0mL of 2.0x10-3M KSCN and 25.00mL of 0.0020M Fe(NO3)3 are diluted to 100.0mL.

Hint: Answer includes 2 significant figures.

Hint: See "PREPARATION OF STANDARD SOLUTIONS" on page 3-2.

Hint:

PREPARATION OF STANDARD SOLUTIONS

To get solutions with known [FeSCN²⁺], the following process will be used. You will prepare standard solutions by mixing carefully measured volumes of solutions of Fe³⁺ (using Fe(NO₃)₃ stock solution) and SCN^– (using KSCN stock solution) of known concentrations. These volumes for standard solutions A–F are listed in the Standard Solutions Table (Table 3-1) in Part A, step 6. The key to getting a known concentration of FeSCN²⁺ in each of these solutions is that the initial concentration of Fe³⁺ is much greater than the initial concentration of SCN^– ion. When the Fe³⁺ concentration is in large excess, the equilibrium will shift (according to Le Châtelier’s Principle) to the product side until virtually all the SCN^– is converted to FeSCN²⁺. Thus the equilibrium concentration of FeSCN²⁺ in a standard solution will be virtually the same as the initial concentration of SCN^– in the solution. This initial value, [SCN^–]_initial, which equals [FeSCN²⁺] in the mixed standard solution, can be calculated from the volume and molarity of the SCN^– stock solution (mol SCN^– = M × V) and the final total volume (in L) of the mixed standard solution. With these calculated values for [FeSCN²⁺] and the measured absorbances of these standard solutions, a Beer’s law plot can be obtained.

Write the balanced equation for the reaction of aqueous Pb (ClO3)2 with aqueous Nal. Include phases

What mass of precipate will form if 1.50L of highly concentrated Pb(ClO3)2 is mixed with 0.400L of 0.110 M Nal?

Part A: Using your graduated cylinder, you calibrate the pipet you will be using and the values you collect are as follow. What is the average number of drops per mL of benzene.

  21 dropsdrops   

 23 dropsdrops   

  17 dropsdrops   

Part B: After calibration, you use the oleic acid/benzene solution to form a monolayer. It takes   6 dropsdrops   ,   9 dropsdrops    and   7 dropsdrops    before the layer on the water solution starts to make a bubble tha does not go into solution. What is the average number of drops for your monolayer?

Part C: Since we have the number of drops it takes to make a monolayer and we have the number of drops it takes to make one mL of benzene, we can determine the mL of oleic acid/benzene it takes to form a monolayer.  

Part D: Next we need to determine the mass of oleic acid in the monolayer. The concentration of the oleic acid/benzene solution is 0.02g/L. Calculate how many grams of oleic acid is in one drop.

Part E: With this information, we now need to calculate the volume in milliliters. We need to know how many mLs a drop of oleic acid occupies using the density of 0.895 g/mL and the number of drops of oleic acid solution used. (answer in mL/Drop)

Part F: Determine the volume of the monolayer from the above information.(in mL)

Part G:Calculate the thinkness of the monolayer assuming that the volume of the monolayer is   7.23×10⁻⁶ mLmL   and diameter of the watch glass is 5 cm.( answer in cm)

Part H: Determine the number of moles of oleic acid in the monolayer. Assume the nubmer of grams of oleic acid in the monolayer is   7.54×10⁻⁶ (answer in Mol)

Part I: Calculate the surface area of one molecue if we assume the molecule is shaped like a cylinder that the hight is 10x larger than the radius.( answer in cm^2)

Part J: Determine the area of the surface covered by the molecues assuming they have a circular surface which at most can cover 90.6%. ( answer in cm^2)

Part K: Calculate the number of molecules in the surface.

Part L: Calculate the number of molecues in 1 mole of calculated oleic acid.

Part M: Compare this number based on the Avogadro's number finding the % error. Discuss why the % error is well over 100% and how that would be possible.

closed

In the Bohr model, when an electron leaves one n orbit and enters another n orbit, a photon is either emitted or absorbed. Derive a relationship between the wavelength of the emitted or absorbed photon and the change in the DeBroglie wavelength of the electron when it moves from one n to another n.

Determine pH for a solution containing 0.7 M HBr and 1.4 M HC₃H₅O₂.

How would you prepare a 1.50 molal solution of sucrose in water? At what temperature would the solution begin to boil?

thank you

You are asked to prepare 1.1L of a HCN/NaCN buffer that has a pH of 9.77 and an osmotic pressure of 1.97atm at 298 K.

What masses of HCN and NaCN should you use to prepare the buffer? (Assume complete dissociation of NaCN.)

......... I put in ( 1.09 ) and ( 1.09 ) but it says its incorrect,,,,, Please Help!!