Recent Homework Questions About Chemistry
A solution contains an unknown amount of dissolved magnesium. Addition of 5.34×10−2mol of Na2CO3 causes complete precipitation of all of the magnesium. What mass of magnesium was dissolved in the solution.
Tuesday, September 30, 2014 at 7:19pm
HELP PLEASE. I have no idea how to set this up. I tried using the q=mc(change in temp) equation but its not working out. A 59.8 g block of an unknown metal at 87.5 degrees Celsius was dropped into an insulated vesssel containing approximately 33 g of ice and 23 g of water at 0...
Tuesday, September 30, 2014 at 7:00pm
a 1.0kg sample of metal with a specific heat of 0.50KJ/Kg C is heated to 100.0C and then placed in a 50.0g sample of water at 20.0C . What is the final temperature of the metal and the water?
Tuesday, September 30, 2014 at 5:31pm
An aqueous stock solution is 85.0% H2SO4 by mass and its density is 1.83 g/mL. What volume of this solution is required to make 1.00 L of 1.35 mol/L H2SO4(aq)? Give your answer in millilitres, accurate to three significant figures.
Tuesday, September 30, 2014 at 4:27pm
Identify the following chemical equations by type. 1. If an electric discharge produces 800 cm3 of ozone (O3), how many cm3 of oxygen (O2) are required? 3O2(g) ---> 2O3(g) 2. When 75.0 dm3 of O2 react with an excess of glucose (C6H12O2), according to the reaction below, ...
Tuesday, September 30, 2014 at 3:05pm
Household bleach contains (NaClO)2 that decomposes in water, NaClO + h2o = Na+ + OH- + Cl2 + O2 If 15ml bleach containing 5.85℅ NaClO is allowed to decomposes completely, then hoe many mL of o2 at 22C and 755mmHg can be liberated. Density of bleach= 1.12g/ml Answer I ...
Tuesday, September 30, 2014 at 1:10pm
Chemistry question: Given: CH4 + 2O2 ~ CO2 + 2H2O C - H = 99 kcal O - O = 119 kcal C = O = 192 kcal O - H = 111 kcal Calculate the change in energy for the CH4 - O2 system.
Tuesday, September 30, 2014 at 9:13am
Accurately weigh 0.9-1.1 g into a 200 mL beaker. Dissolve the KIO3 in a small amount of distilled water. Quantitatively transfer, with rinsing, to a 500 mL volumetric flask. Dilute to the calibration mark and shake well. Rinse the buret several times with small portions of the...
Tuesday, September 30, 2014 at 9:02am
A mixture of 2.5 moles of H2O and 100 g of C are placed in a 50.0 L container and allowed to come to equilibrium in the following reaction: C(s) + H2O(g) CO(g) + H2(g) The equilibrium concentration of hydrogen gas is found to be 0.040 M. What is the ...
Tuesday, September 30, 2014 at 1:21am
Consider the following reaction at equilibrium: 4NH3(g) + 5O2(g) ↔ 4NO(g) + 6H2O(g) In what direction will the following changes force the reaction? a) Addition of O2 b) Reduction of the amount of water vapour c) Increase in the pressure d) Decrease in the volume e) If ...
Tuesday, September 30, 2014 at 1:19am
PLEASE CHECK! ELA
Which word group is a complete sentence? A- Almost all the swimmers following the rules. B- Never had any interesting activities. C- After Chris finished chemistry experiment. D- Only two of the chairs matched the table. My guess is D.
Monday, September 29, 2014 at 10:32pm
Chemistry- Answer Check
In an ideal gas, if only one molecule in a thousand has enough energy to react, how can all molecules in a reactor be consumed? My answer: when the one molecule reacts, it causes the other molecules to gain energy. Is this right? I'm still confused on the question
Monday, September 29, 2014 at 10:03pm
A solution contains 5.6g of solute in 16 cm cubed of water. When the solution is cooled, crystals begin to appear at 11 degrees celsius. What is the solubility of the solute at 11 degrees celsius?
Monday, September 29, 2014 at 9:19pm
The density of silver is 1.050×104 kg/m3. What is the mass of a rectangular ingot of silver with dimensions 1.00 cm × 4.00 cm × 0.780 dm? How do I get started? I really do not understand.
Monday, September 29, 2014 at 7:48pm
we would build one spectrometer apparatus with webcam to analyze two different beers based on yeast or bitterness so which one would be easy/less time to analyze yeast or bitterness ? please expalin why :S
Monday, September 29, 2014 at 6:50pm
Chemistry - Titrations
What volume (mL) of 0.2650 N H3PO4 is required to neutralize: a) 35.25 mL of 0.2300 M KOH b) 19.14 mL of 0.2300 M NH4OH Unfortunately, the teacher didn't get the opportunity to teach us titrations in class today, but this problem (and more) are still due by 11 pm tonight (...
Monday, September 29, 2014 at 6:02pm
Chemistry: Please check my answer
ClO2 is sometimes used as a chlorinating agent for water treatment. Cl2 + 4 NaClO -> 4 NaCl + 2 ClO2 In an experiment, 1L Cl2 measured at 10C and 4.66atm is dissolved in .75L of 2.00M NaClO. If 25.9g of pure ClO2 is obtained, then what is the percent yeild for this ...
Monday, September 29, 2014 at 4:59pm
Al and Fe react with HCl to produce a chloride salt and hydrogen gas. A .1924g sample of a mixture of Al and Fe is treated with excess HCl solution. A volume of 159mL h2 gas is collected over water at 19C and 841 torr. What is the mass percent by mass of Fe in the mixture? The...
Monday, September 29, 2014 at 2:21pm
A mixture of 3.00 g of silver and copper metals was dissolved in excess nitric acid. Resulting salts, silver(I) nitrate and copper(II) nitrate, were isolated and dissolved in enough water to make 0.100 L of a solution with a total concentration of the nitrate ion equal to 0....
Monday, September 29, 2014 at 11:42am
A 0.160 M solution of an enantiomerically pure chiral compound D has an observed rotation of 0.20° in a 1-dm sample container. The molar mass of the compound is 128.0 g/mol. (a) What is the specific rotation of D? (b) What is the observed rotation if this solution is mixed...
Monday, September 29, 2014 at 10:13am
A 36.1 mL sample of oxygen gas contains 0.529 mol of oxygen. If enough oxygen is added to the sample to obtain a volume of 50.5 mL, what must the final mass of the sample be? (The pressure and temperature is constant.)
Monday, September 29, 2014 at 3:02am
Dr.Bob222 please help given the following table of thermodynamic data substance delta HofF S PCl3 -288.07 kJ/mol 311.7 J/mol-k PCl3 -319.6 kJ/mol 217 J/mol- k determine the normal boiling point (C)of PCl3
Monday, September 29, 2014 at 1:43am
What is the difference between Citric Acid C6H8O7 and H3C6H5O7? I am seeing both and don't know which is the right one. Is one a solution of citric acid? Thanks
Monday, September 29, 2014 at 1:02am
A 55.29-g sample of Ba(OH)2 is dissolved in enough water to make 1.20 L of solution. How many milliliters of this solution must be diluted with water in order to make 1.00 L of 0.100 M Ba(OH)2? (Ignore significant figures for this problem.)
Sunday, September 28, 2014 at 11:58pm
During recrystallization, an orange solution of a compound in hot alcohol was treated with activated carbon and then filtered through fluted paper. On cooling, the filtrate gave gray crystals, although the compound was reported to be colorless. Explain why the crystals were ...
Sunday, September 28, 2014 at 9:41pm
a 6 g sample of magnesium was burned in a crucible producing 10 g of magnesium oxide. What mass of oxygen reacted with magnesium to form the 10 g of magnesium oxide?
Sunday, September 28, 2014 at 9:10pm
What is the molar concentration of all ions present in a solution prepared by mixing the following? Assume that volumes of the solutions are additive, and neglect H+ and OH- from water. 60.0 mL of 0.25 M KCl and 80.0 mL of 0.85 M NaOH.
Sunday, September 28, 2014 at 5:23pm
Aluminum sulfate reacts with calcium hydroxide (from lime) to form aluminum hydroxide and calcium sulfate. Write the balanced formula unit equation for the reaction.
Sunday, September 28, 2014 at 5:10pm
A .7178 g sample of a hydrocarbon occupies a volume of 390.7 mL at 65C and 99.2kpa. When the sample is burned in excess oxygen, 2.4267 g CO2 and .4967g H2O are obtained. What is the molecular formula of the hydrocarbon? Write a plausible structural formula for the molecule. ...
Sunday, September 28, 2014 at 3:51pm
If He(g) has an average kinetic energy of 7590 J/mol under certain conditions, what is the root mean square speed of F2(g) molecules under the same conditions?
Sunday, September 28, 2014 at 3:47pm
how many moles of oxygen are there in 50.0 grams of KClO3? Given: 50.0 g KClO3 Find: ? mol O K= 39.10 g/mol Cl= 35.45 g/mol O= (16.00)x3= 48.00 g/mol Total: 122.55 g/mol KClO3 50.0 g KClO3 x 1 mol KClO3/122.55 g/mol KClO3=0.408 mol KClO3 0.408 mol KClO3 x 3(oxygen)=1.22 moles O
Sunday, September 28, 2014 at 3:36pm
A sample of unknown metal has a mass of 36.7 g. This metal was placed in boiling water at 96.0oC until the metal had reached the temperature of the water. The metal was then placed in a foam cup with 50.0 g of water in it at 20.0oC. The cup absorbs 42.0 J/oC, and the ...
Sunday, September 28, 2014 at 2:46pm
heat lost by metal + heat gained by water = 0 [mass metal x specific heat metal x (Tfinal-Tinitial)] + [mass water x specific heat water x (Tfinal-Tinitial)] = 0 Substitute and solve for specific heat metal.
Sunday, September 28, 2014 at 2:16pm
21.90 kJ/g x 0.1182 g = ?q = energy obtained by combusting salicylic acid. Then calculate the heat capacity of the calorimeter. That is q from above = C/degree c x 2.84 and solve for C, the heat capacity of the calorimeter. q = heat capacity x delta T q = Cfrom above x 3.50 ...
Sunday, September 28, 2014 at 2:15pm
Balance following oxidation reduction reactions using oxidation states method? a) Cl2(g) + Al(s) --> Al3+(aq) + Cl- b.) O2(g) + H2O(l) + Pb(s) --> Pb(OH)2(s) c) H+(aq) + MnO4-(aq) + Fe2+(aq) --> Mn2+(aq) + Fe3+(aq) + H2O(l)
Sunday, September 28, 2014 at 12:55pm
2. The half-life of a radioactive element is important when considering its application in medicine. For example, iodine-131 is often used in the imaging of the thyroid. The reason is that iodine is readily absorbed by the thyroid gland. Another reason is the short half-life ...
Sunday, September 28, 2014 at 12:31pm
A sample of gas occupies 17mL at -112 degrees Celsius. Assuming the pressure is held constant, what volume does the sample occupy at 70 degrees Celsius?
Sunday, September 28, 2014 at 12:03pm
Use half-cells to balance the following redox reaction, and label the oxidation and reduction half-reactions. Also, note that bromide is a spectator ion and can be eliminated. FeBr(aq) +Mg(s) = Fe(s) + MgBr2(aq) Fe^+2 -2e +Br^- e+ + Mg^+2 -2e =Fe^+2 -2e +MgBr2(aq) -2e e+ Idk ...
Sunday, September 28, 2014 at 11:32am
GE's light bulb division ordered 100.kg of tungsten for the filaments. If the tungsten comes in a cube what is the volume of the cube? What is the length of each side?
Sunday, September 28, 2014 at 8:43am
The structure of tryptophan is shown at the right along with the pK values of the α-carboxyl and α-amino groups. (pK1=2.38; pK2=9.39) Tryptophan is a diprotic acid which can exist in three protonated forms: H2A , HA0, and A. (HA0 consists primarily of the ...
Sunday, September 28, 2014 at 8:32am
I what this question to be solve.what will be the pressure of 50cm^3 of oxygen gas in a piston initially at a pressure of 2atm when the volume was 500cm^3 at a steady temperature of 300k
Sunday, September 28, 2014 at 8:01am
Chemistry- colligative properties
Which of the following aqueous solution of equal molality has the lowest freezing point? a. H2SO3 b. NaCl c. NaOH d. Ca(NO3)2 How do you answer this without looking at their i values from textbooks? I know that delta(Fpt) = m * K,f * i and that i is approximately equal to the ...
Sunday, September 28, 2014 at 6:08am
A Power plant rated at 800 MegaWatts generates steam at 585 K and discards heat to a river at 295 K. If thermal efficiency of plant is 70% of maximum value, how much heat is discarded to river at rated power? Please help with steps on how to solve this one.
Sunday, September 28, 2014 at 6:03am
If He(g) has an average kinetic energy of 7590 J/mol under certain conditions, what is the root mean square speed of F2(g) molecules under the same conditions?
Sunday, September 28, 2014 at 3:43am
The complete combustion of salicylic acid releases 21.90 kJ of energy per gram of salicylic acid. In a particular bomb calorimeter (initially at room temperature), the combustion of 0.1182 g of salicylic acid, in the presence of excess oxygen, causes the temperature of the ...
Saturday, September 27, 2014 at 10:00pm
Hydrogen gas produced by this reaction is typically collected via water displacement, during which time the hydrogen gas becomes saturated with water vapor. If 238.4 mL of gas with a total pressure 1.27 atm was collected via water displacement at 29.4 °C, what is the ...
Saturday, September 27, 2014 at 9:55pm
30 ml of sample of unknown strong base is neutralized after the addition of 12 ml of a 0.150 M HNO3 solution if the unknown base concentration 0.0300 M give the possible identities for the unknown base
Saturday, September 27, 2014 at 9:47pm
If you dilute 14.0mL of the stock solution to a final volume of 0.350L , what will be the concentration of the diluted solution? Before it, there was a question: How many milliliters of a stock solution of 5.60 M HNO3 would you have to use to prepare 0.190L of 0.450 M HNO3? ...
Saturday, September 27, 2014 at 9:12pm
Imagine there is a tank of unknown gas that contains 53.31% carbon, 35.51% oxygen, and 11.18% hydrogen by mass. At 35.0 °C and 0.470 bar, 2.0 L of the gas has a mass of 3.3 g. Using this information, answer the following questions. a.) What is the empirical formula of the ...
Saturday, September 27, 2014 at 7:07pm
A 8.50-g sample of solid AlCl3·6H2O was heated such that the water turned to steam and was driven off. Assuming ideal behavior, what volume would that steam occupy at 1.00 atm and 100.0 °C?
Saturday, September 27, 2014 at 7:04pm
A 8.80-g sample of solid SnCl2·2H2O was heated such that the water turned to steam and was driven off. Assuming ideal behavior, what volume would that steam occupy at 1.00 atm and 100.0 °C?
Saturday, September 27, 2014 at 6:46pm
Suppose 1.2x10^3 kg of C is mixed with 2.4x10^5g oxygen gas and carbon dioxide forms. 1. write the reaction and balance 2.which reactant is the limiting reagent and which reactant is in excess 3. How many grams of carbon dioxide will be formed.
Saturday, September 27, 2014 at 5:40pm
2NiS2(s)+5O2(g)=2NiO(s)+4SO2(g) 1. how many kilograms of NiO would be formed from the reaction of .0125 mol of NiS2? 2. How many grams of O2 are needed to cmpletely react with 3.74 g of NiS2.
Saturday, September 27, 2014 at 5:38pm
a student mixes 4 reagents together thinking that the solution will neutralize each other . The solution is mixed together are 50 ml of 0.100 M of HCL and 100 ml of 0,200 M of nitric acid 500 ml of 0.0100 M ca hydroxide and 200 ml of 0.100 M rubidium hydroxide . Did the acid ...
Saturday, September 27, 2014 at 3:41pm
The half-life of oxygen-15 is 124 s. If a sample of oxygen-15 has an activity of 4800 Bq, how many minutes will elapse before it has an activity of 600 Bq?
Saturday, September 27, 2014 at 3:37pm
Please help! Calculate the standard change in enthalpy, ΔH°rxn, for the decomposition of calcium carbonate to calcium oxide CaCO3 (s) → CaO (s) + CO2 (g) Given that: ΔH°f CaCO3 (s) = -1206.9 kJ/mol ΔH°f CaO (s) = -635.1 kJ/mol ΔH°f CO2...
Saturday, September 27, 2014 at 3:20pm
Please help me! I don't know how to do this at all. Calculate the enthalpy for the reaction: NO (g) + O (g) → NO2 Given the following known reactions: NO(g)+O3 (g)→NO2 (g)+O2 (g) 03 (g)→1.5O2 (g) O2 (g)→2O(g) ΔH°=-198.9kJ ΔH°=-142....
Saturday, September 27, 2014 at 2:25pm
in HNO3 titration, you add few drops of phenolphthalein indicator to 50.0 mL of acid in a flask. you quickly add 20.00 mL of 0.0547 M NaOH but overshoot the end point, and the solutions turn deep pink. instead of starting over, you add 30.00 mL of acid, and the solution turns ...
Saturday, September 27, 2014 at 6:53am
A 4.78-g sample of aluminum completely reacts with oxygen to form 6.67 g of aluminum oxide Use this data to calculate the mass percent composition of aluminum in aluminum oxide. (Sorry need help with this!)
Saturday, September 27, 2014 at 3:07am
Bones are mostly calcium phosphate. Calcium chloride reacts with potassium phosphate to form calcium phosphate and potassium chloride. Indicate the physical states or reactants and products a) Write the balanced equation of the information above b) Determine the total ionic ...
Friday, September 26, 2014 at 10:18pm
An electrical heater delivers 4.070 kJ of energy (as heat) to a system consisting of the gas inside a cylinder having a movable piston. As a result, the piston moves against a constant external pressure such that P ∆V = 2.442 kJ. What is the change in internal energy for...
Friday, September 26, 2014 at 7:39pm
Use the following values for the arrows in the drawing: a = 185 J of heat; b = 45 J of heat; c = 115 J of work; d = 40 J of work; e = 65 J of work; and f = 190 J of heat. Find the change in the internal energy of object A only. Use the First Law of Thermodynamics Be careful ...
Friday, September 26, 2014 at 5:02pm
Dalton discovered electrons inside of atoms by using thermal energy. Thompson discovered electrons inside of atoms by using cathode rays. Thompson discovered electrons inside of atoms by using X rays. Dalton discovered electrons inside of atoms by using cathode rays. Dalton ...
Friday, September 26, 2014 at 4:19pm
Chemistry of Life
Which statement is true about water molecules? The oxygen atom has a negative charge. The hydrogen atoms do not share electrons. Water molecules move randomly around each other. Water molecules cannot dissolve many substances. Question 2. How does water relate to the ability ...
Friday, September 26, 2014 at 4:13pm
An aqueous solution of barium nitrate has a density of 1.09 g/cm3. The solution is 18.7% barium nitrate by mass. How many nitrate ions are present in 87.6 dL of this solution?
Friday, September 26, 2014 at 12:23pm
My head is spinning from this chapter! I've done most of the questions by myself but I have no idea what formulas I should use for these last two. Can you walk me through them so I can understand what I need to do? 1. What volume of 5.0 M HNO3 is required to neutralize ...
Friday, September 26, 2014 at 2:07am
Use solubility rules to write the balanced molecular, complete ionic, and net ionic equations for the aqueous reaction between BaI2 and Hg(NO3)2. Include phase subscripts on all substances. I got to the part where you switch the elements Ba(NO3)2 +HgI2 I don't know where ...
Thursday, September 25, 2014 at 9:17pm
A 23.0-g sample of an unknown metal is heated to 91.5°C and is placed in a perfectly insulated container along with 102.g of water at an initial temperature of 21.80°C. After a short time the temperature of both the metal and water become equal at 23.80°C. The ...
Thursday, September 25, 2014 at 7:24pm
The heat lost or gained by a system is related to its temperature change by a property called its heat capacity. The molar heat capacity of metals at or above room temperature equals 24.92 J/K.mol. The temperature of a block of lead (MM 207.2) was raised by 13.1 degrees when ...
Thursday, September 25, 2014 at 7:15pm