What answer should be reported, with the correct number of significant figures, for the following calculation? (249.362 + 41)/63.498 Please explain the significant figures portion.

Given the values of ?H?rxn, ?S?rxn, and Tbelow, determine ?Suniv. Also, predict whether each reaction will be spontaneous or nonspontaneous

A)?H?rxn= 86kJ , ?Srxn= 142J/K , T= 308K

Express your answer using two significant figures.

B)?H?rxn= 86kJ , ?Srxn= 142J/K , T= 762K

Express your answer using one significant figure.

C)?H?rxn= 86kJ , ?Srxn=? 142J/K , T= 308K

Express your answer using one significant figure.

D)?H?rxn=? 86kJ , ?Srxn= 142J/K , T= 404K

Express your answer using one significant figure.

Determine the pH during the titration of 36.0 mL of 0.235 M trimethylamine ((CH₃)₃N, K_b = 6.3×10^-5) by 0.235 M HBr at the following points. (Assume the titration is done at 25 °C.)
Note that state symbols are not shown for species in this problem.

a.) Before the addition of any HBr

b.) After the addition of 15.3 mL of HBr

c.) At the titration midpoint

d.) At the equivalence point

e.) After adding 56.2 mL of HBr

Al(s) + HCl(aq) → AlCl3(aq) + H2(g) 2. According to the equation above, how many grams of aluminum are needed to completely react with 2.19 mol of hydrochloric acid? 3. Sulfur dioxide will react with water to form sulfurous acid SO2(g) + H2O(l) → H2SO3(l) What mass of sulfur dioxide is needed to prepare 27.86 g of H2SO3(l)? 4. The compound P4S3 is used in matches. It reacts with oxygen to produce P4O10 and SO2. The chemical equation is shown below. P4S3(s) + O2(g) → P4O10(s) + SO2(g) What mass of SO2 is produced from the combustion of 0.401 g P4S3? 5. How many moles of Mg3P2(s) can be produced from the reaction of 0.14 mol Mg(s) with 0.020 mol P4(s)? Mg(s) + P4(s) → Mg3P2(s) 6. A 5.95-g sample of AgNO3 is reacted with excess BaCl2 according to the equation AgNO3(aq) + BaCl2(aq) → AgCl(s) + Ba(NO3)2(aq) to give 4.48 g of AgCl. What is the percent yield of AgCl? 7. Sulfur hexafluoride is produced by reacting elemental sulfur with fluorine gas. S8(s) + F2(g) → SF6(g) What is the percent yield if 18.3 g SF6 is isolated from the reaction of 10.0 g S8 and 30.0 g F

how do you determine the number of hydrogen atoms bonded to each carbon in a line-angle formula?

Calculate the millimoles of sodium hypochlorite used in the reaction: 5 mL of a 5.25% solution of Clorox bleach (show detailed calculations). Compare this value with the quantity of diphenylmethanol (millimoles) to be used in the reaction. Would you describe the oxidant as being present in slight excess or large excess?

For H35Cl (ΘV = 4304 K) what is the approximate contribution of vibrational degrees of freedom to the molar constant volume heat capacity at 298 K?

In an adiabatic, constant-volume bomb calorimeter, a combustion of 0.7362g of naphthalene (C10H8) caused the temperature to rise of 5.707 Celcius. The final temperature was 298.000K. The heat capacity of the calorimeter, Ccal was 10290 J/K . (Note: this value of Ccal includes the contribution from water.) The molar enthalpies of formation of CO2(g) and H2O(l) are: -393.522 kJ/mol, -285.830 kJ/mol, respectively Mm(C)= 12.01 g/mol and Mm(H)= 1.001 g/mol.

a.) Calculate deltaUc , deltaUcm , delta Hcm for this combustion reaction.

b.) What are delta Hf and delta Hfm of naphthalene?

A 27 mL solution of .100 M CH3COOH is titrated with a .220 M KOH solution. Calculate the pH after the following additions of the KOH solution:

a) 0 mL

b) 5 mL

what effect would each of the following have on the calculated molar mass of an unknown?

a) The balance was not zeroed before the three weighings of the test tube, sample, water were made. This caused each mass measurement to be 0.102 g greater than it should have been.

b) The thermometer consistently read 0.06 C lower than it should have, over the entire experimental range

c) The masses of the unknown and the solvent (water) were determinded, and the unknown completely dissolved in the water. Just before the jacketed test tube containing the unknown solution was placed in the ice-salt water bath, a small amount of the solution was spilled out of the tube.

d) The unknown contained a smal amount of an insoluble impurity

e) The unknown contained a small amount of a soluble impurity, which had a molar mass lower than that of the pure unknown.

f) A portion of the unknown did not dissolve.

A certain person had a brain that weighed 1.10 kg and contained 3.51 x 10^10 cells. Assuming that each cell was completely filled with water (density = 1.00 g/mL) calculate the length of one side of such a cell if it were a cube.

If the surface were spread out into a thin layer that was a single cell thick what would be the surface area in square meters?

Determine the theoretical yield and the percent yield if 21.8 g of K2CO3 is produced from reacting 27.9 g KO2 with 29.0 L of CO2 (at STP).   The molar mass of KO2 = 71.10 g/mol and K2CO3 = 138.21 g/mol.

Consider the reaction that converts pyruvic acid (CH3COCOOH) into gaseous acetaldehyde (CH3CHO) and gaseous CO2, which is catalyzed in aqueous solution by the enzyme pyruvate decarboxylase. Assume ideal gas behavior for CO2.

Calculate ?rG (298 K) for this reaction at 160 bar.

A 50 mm internal diameter horizontal steel pipe carrying steam is covered by a 50 mm thick layer of a ceramic insulation material and is tightly wrapped with a 0.5 mm thick layer of clean aluminum foil. The wall thickness of the steel pipe is 3.9 mm. The entire pipe is surrounded by air at 20°C. The emissivity of the aluminum foil can be taken as 0.05. Determine the steady-state temperature of the outside surface of the aluminum foil if the temperature of the inner surface of the steel tube is 122°C. The thermal conductivity values are: for steel: 45 W/(m.K), for the insulation: 0.07 W/(m.K); for aluminum foil: 167 W/(m.K). {Hint: you have to account for both convective and radiation heat loss to the surroundings.}