nstant cold packs sometimes used to treat athletic injuries contain solid ammonium nitrate and liquid water separatedbya thin divider. When the divider is broken, the ammonium nitrate dissolves endothermically:

NH4NO3(s) NH4+(aq) + NO3–(aq)

To measure the enthalpy of this reaction, you dissolve 1.25 g of ammonium nitrate in enough water to make 25.0 mL of solution. The initial temperature is 25.8 °C, and the final temperature is 21.9 °C. (Assume that the density of the solution is 1.00 g /mL and that the heat capacity of the solution is 4.184 J/g∙°C

A student mixes 5.00 mL of 2.00 x 10‐3 M Fe(NO3)3 with 5.00 mL 2.00 x 10‐3 M KSCN. She finds that in the equilibrium mixture the concentration of FeSCN+2 is 1.40 x 10‐4 M.

What is the initial concentration in solution of the Fe+3 and SCN‐?

What is the equilibrium constant for the reaction?

What happened to the K+ and the NO3‐ ions in this solution?

How many grams of O2 can be prepared from the thermal decomposition of 4.09kg of H2O

Titration: calculate (a) the initial pH, (b) the volume and the pH at 1/3 of the equivalence point, (c) the volume and the pH at 2/3 of the equivalence point, (d) the volume and the pH at 99/100 of the equivalence point, (e) the volume and the pH at the equivalence point, (f) the volume and the pH at 101/100 of the equivalence point, (g) the volume and the pH at 4/3 of the equivalence point, and (h) the volume and the pH at 5/3 of the equivalence point. The initial volume of acid is 1.00 L. Using 1.00L 0.2217M HIO Ka=2.3x10^-11 Titrated with 0.1443M KOH

Consider the following unbalanced redox reaction

CrO₄^2- + (CH₃)H + H⁺ → Cr³⁺ + HCOOH + H₂O

Which of the following statements is/are correct?

1.CrO₄^2- is the oxidizing agent.

2. The oxidation number of Cr is decreased in the redox reaction.

3. Electrons are released from CrO₄^2-

• A. 1 only
• B. 1 & 3 only
• C. 2 & 3 only
• D. 1 & 2 only
• E. all

Juice is put into bottles and sealed. Each bottle contains 1500 mL of product and has 65 mL headspace of air with 20% by volume of oxygen in it. The specific gravity of the product is 1.04.

During packaging, the dissolved oxygen content of the product is 7.0 ppm. The juice concentrate contributes 5.5 mg Vitamin C per 100 mL to the final product mixture. The processor then adds an unknown amount of vitamin C to the product to bring it to the desired concentration after storage. After storage, the Vitamin C content of the product falls to 55 mg per 100 mL.  15.7mg of Vitamin C are needed to consume 1mL of oxygen.

How much Vitamin C (in grams) would the processor need to add to make enough beverage to fill 1,000 bottles?

1. From an evolutionary perspective, why does the fermentation pathway exist?
2. Given that generating pyruvate gives net 2 ATPs, what is the biochemical rationale for converting pyruvate to lactate?

Explain why ICP-MS is more sensitive than ICP-AES.

Calculate the pH of the solution that results from each of the following mixtures.

140.0mL of 0.26M HF with 220.0mL of 0.30M NaF

Producing polymers with high molecular weights is difficult in step polymerizations. Why is it difficult and which techniques exist to overcome this difficulty?

Determine the pH during the titration of 56.9 mL of 0.385 M hydrofluoric acid (Ka = 7.2×10-4) by 0.385 M NaOH at the following points.

(a) Before the addition of any NaOH

(b) After the addition of 14.0 mL of NaOH

(c) At the half-equivalence point (the titration midpoint)

(d) At the equivalence point

(e) After the addition of 85.4 mL of NaOH

When 50.0 mL of 60.0°C water was mixed in the calorimeter with 50.0 mL of 25.0°C water, the final temperature was measured as 40.8 °C. Assume the density for water is 1.000 g/mL regardless of temperature.

a. Determine the magnitude of the heat lost by the hot water.

b. determine the magnitude of the heat gained by the room temperature water.

c. determine the heat gained by the calorimeter

d. determine the calorimeter constant.

As a chemist for an agricultural products company, you have just developed a new herbicide,"Herbigon," that you think has the potential to kill weeds effectively. A sparingly soluble salt, Herbigon is dissolved in 1 M acetic acid for technical reasons having to do with its production. You have determined that the solubility product Ksp of Herbigon is 9.50×10−6. Although the formula of this new chemical is a trade secret, it can be revealed that the formula for Herbigon is X-acetate (XCH3COO, where "X" represents the top-secret cation of the salt). It is this cation that kills weeds. Since it is critical to have Herbigon dissolved (it won't kill weeds as a suspension), you are working on adjusting the pH so Herbigon will be soluble at the concentration needed to kill weeds. What pH must the solution have to yield a solution in which the concentration of X+ is 6.00×10−3 M ? The pKa of acetic acid is 4.76.

A concentration cell based on the following half reaction at 312 k ag+ + e- --------> ag srp = 0.80 v has initial concentrations of 1.25 m ag+, 0.221 m ag+, and a potential of 0.04865 v at these conditions. after 8.3 hours, the new potential of the cell is found to be 0.01323 v. what is the concentration of ag+ at the cathode at this new potential? Please explain all the steps used to find the answer.