General Chemistry Answers

How many grams of potassium chloride are produced if 15 grams of potassium chlorate decomposes?"

Which of these changes are endothermic? Which are exothermic? (You must know the names for each of the phase changes.) please explain

a) Melting of ice

b) CH4 (g) + 2 O2 (g) --> CO2 (g) + 2 H2O (g) + 882 kJ

c) Deposition of iodine

d) NH4Cl (s) --> NH4Cl (aq) ΔH° = + 14.7 kJ/mol

e) Calcium oxide solid dissolving in water causes a temperature increase

Which of these changes are endothermic? Which are exothermic? (You must know the names for each of the phase changes.)

a) Water accumulating on grass early in the morning

b) Solidification of liquid magma

c) 3NO2 + H2O --> 2HNO3 + NO ∆H = - 138 kJ

d) 6CO2 + 6H2O + 2803 kJ --> C6H12O6 + 6O2

e) Sugar crystalizing in a saturated solution.

1. What is the sign and magnitude of the heat associated with a process with 342 J of work is done and there is an increase in the internal energy of 5.43 kJ?
2. What is the sign and magnitude of the work associated with a process where the system lost 1.23 kJ of heat and the internal energy was reduced by 921 J?
3. The volume of a balloon expands by 230 mL against an atmospheric pressure of 745 mm Hg. Assuming the resistance of the latex to be negligible, how much work is associated with the process?

1. How much heat is released when 9.22 grams of glucose C6H12O6 reacts according to the following equation?

C6H12O6 + 6O2 --> 6CO2 + 6H2O ∆H = -2803 kJ

2. How much heat is absorbed during photosynthesis when 9.22 grams of glucose C6H12O6 is produced?

6CO2 + 6H2O --> C6H12O6 + 6O2 ∆H = +2803 kJ

3. How much heat is released when 147 grams of NO2(g) is dissolved in excess water?

3NO2 + H2O --> 2HNO3 + NO ∆H = - 138 kJ

4. Calculate the heat released when 74.6 grams of SO2 reacts according to the following equation.

2SO2 + O2 --> 2SO3 ∆H = -99.1 k

1. A chemistry student added 22.5 grams of aluminum at 85.00C to 115 grams of water at 23.00C in a perfect calorimeter. The final temperature of the aluminum-water mixture was 41.40C. Use the student’s data to calculate the specific heat of aluminum in joules/gram0C.

2. Calculate the final temperature that results from mixing 100.0 grams of water at 1000C with 106.0 grams of water at 24.80C

A sample of gas has a mass of 38.7 mg. Its volume is 220 mL at a temperature of 54 ∘C and a pressure of 897 torr. Find the molar mass of the gas. Express your answer in grams per mole to three significant figures. 

At certain temperature a 1.0 L flask initially contained 0.298mol PCl3(g) and 8.7 x 10-3 mol PCl5(g). After the system had reached equilibrium, 2.00 x 10-3 mol Cl2(g) was found in the flask. Gaseous PCl5(g) decomposes according to the reaction:

   PCl5(g)                    PCl3(g) + Cl2(g)

Calculate the equilibrium concentration of all species and the value of K.

The reaction will proceed in the forward direction

A mixture of CH4 and H2O is passed over a nickel catalyst at 1000K. The emerging gas is collected in a 5.00L flask and is found to contain 8.62g of CO, 2.60g of H2, 43.0g of CH4 and 48.4g of H2O. Assuming that equilibrium has been reached, calculate Kc and Kp for the reaction.

2N_{2 (g)} +5O_{2 (g)} +2H₂ O_(l)  4HNO_{3 (aq)}, ΔH₁ = -255 kJ

Η_{2 (g)} + 1/2O_{2 (g)} H₂O_{( l)}, ΔH₂ = - 256 kJ

S_(s) + H_{2 (g)} +2O_{2 (g)}  H₂SO_{4 (aq)}, ΔH₃ = - 814 kJ

N_{2 (g)} + 2O_{2 (g)}  2NO_{2 (g)}, ΔH₄ = +66 kJ

Να υπολογίσετε την πρότυπη ενθαλπία της αντίδρασης:

6HNO _(aq) + S_(s)  H₂ SO_{4 (aq)} 6NO _(g) 2H₂ O _{(l )}

Suppose you wanted to analyse the amount of metal in alloy. For example, you might want to determine the nickel (Ni2+) content in alloy material.

(a) Using gravimetric analysis, propose precipitating method to analyze nikel (Ni2+) in alloy and write 8 steps required during the precipitation. Also suggest an appropriate solvent and its ratio to dissolve the mixture. Here we recommended to use dimethylglyoxime (H2DMG) as organic precipitating agent. (10 Marks)

(b) Suppose the nickel had been precipitated from the alloy (2.0980g) using dimethylglyoxime (H2DMG) as organic precipitating agent and giving a precipitate of complex nickel dimethylglyoxime (Ni(HDGMG)2) weighing 0.2370g. Calculate the percentage weight of nickel (Ni2+) in the alloy sample. (5 Marks)