Recent Homework Questions About Chemistry
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
I've been trying to figure this problem out all day and I STILL don't know how to solve for the specific heat constant. I blank after I set up the problem. Somebody please help me!!! What is the specific heat constant if 621 g of Metal A raises the temperature of 500.0...
Thursday, September 25, 2014 at 7:12pm
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 ...
Thursday, September 25, 2014 at 4:55pm
The specific heat capacity of gold at 25°C is 1.290×10-1 J/g/K. For a 5.25×102 g sample of gold, how much will the temperature increase if 6.908×102 J of energy is put into the system? (Assume that the heat capacity is constant over this temperature range.)
Thursday, September 25, 2014 at 4:54pm
Anyone know how to go about the problem? I don't know how to do it. Assume a professor has a daily special request for her coffee. She likes to have the 250.0 mL of coffee frozen at -15.0°C overnight and then wants it heated to 95°C when she gets there in the ...
Thursday, September 25, 2014 at 4:26pm
Please help me! I do not know what to do. 500.0 g ethyl alcohol at 25°C (C = 2.46 J/g x °C) absorbs 74.0 J of heat energy. What is the final temperature? What is the specific heat constant if 621 g of Metal A raises the temperature of 500.0 g of water by 3.20°C and...
Thursday, September 25, 2014 at 4:07pm
I'm really confused about how to do these two problems. Please help me. What is the amount of heat (kJ) required if 64.0 kg of H2O is heated from 25°C to 85°C? 200.0 g Al (C = 0.900 J/g × °C) at 95°C is added to 85.4 g H2O at 25°C. What is the ...
Thursday, September 25, 2014 at 3:46pm
PLEASE help because I'm really confused on how to do the entire thing. I don't know how to find the mL. Am I suppose to do anything with the 250mL? A person stops in every day and orders 250 mL of house coffee at precisely 95°C. but enough milk at 10°C to drop ...
Thursday, September 25, 2014 at 2:34pm
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.
Thursday, September 25, 2014 at 12:48pm
If someone has the time to help with the following question it would be really helpful. The problem is 209/83bi+64/28NI=272/111Rg+1/0n How to calculate the energy change in J/mol reactants? AMU amounts: Bi=208.980384 Ni= 63.927969 Rg=272.1535 What I have done is 1. subtract ...
Thursday, September 25, 2014 at 12:25pm
what mass of silver chloride can be prepared by the reaction of 100 ml 0,20 M of silver nitrate with 100,0 ml of 0.15 M calcium chloride calculate the concentration of each ion reamaining in solution after the precipitation is complete
Wednesday, September 24, 2014 at 11:44pm
what mass of barium sulfate can be produced when 100 ml 0.100 M of solution of barium chloride is mixed with 100.0 ml of a 0.100 M solution of Iron (III) sulfate
Wednesday, September 24, 2014 at 11:26pm
A scientist wants to make a solution of tribasic sodium phosphate, Na3PO4, for a laboratory experiment. How many grams of Na3PO4 will be needed to produce 400mL of a solution that has a concentration of Na+ ions of 1.10M ?
Wednesday, September 24, 2014 at 10:29pm
Four isotopes of Lead occur naturally: 204Pb (mass = 203.973037 amu) 206Pb (mass = 205.974455 amu) 207Pb (mass = 206.975885 amu) 208Pb (mass = 207.976641 amu) If the percent abundance of 204Pb and 208Pb are 1.400 and 52.40, respectively, what is the percent abundance of 206Pb...
Wednesday, September 24, 2014 at 10:05pm
In lab, we were finding the distribution coefficient for propanoic acid and ethyl acetate. As well as propanoic acid and toluene. How would you write the chemical equation for the reaction of propanoic acid and ethyl acetate? I know it produces water in the end...but I am not ...
Wednesday, September 24, 2014 at 8:28pm
Three isotopes of Argon occur naturally: 36Ar (mass = 35.9675 amu) 38Ar (mass = 37.9627 amu) 40Ar (mass = 39.9624 amu) If the percent abundance of 36Ar is 0.3400, what is the percent abundance of 40Ar?
Wednesday, September 24, 2014 at 8:17pm
6 small glass beads are found to weigh 9.34 g. The beads are placed in a graduated cylinder filled with ethyl alcohol (density 0.78 g/mL). The reading of the liquid in the cylinder before the beads were added is 21.5 mL. After the beads sink to the bottom of the alcohol the ...
Wednesday, September 24, 2014 at 7:50pm
Assume that the width of your body (across your shoulders) is 50.8 cm inches and the depth of your body (chest to back) is 25.0 cm. If the atmospheric pressure is 14.9lb/in^2, what mass of air (lb) does your body support when you are in an upright position?
Wednesday, September 24, 2014 at 6:36pm
For the reaction shown, find the limiting reactant for each of the following initial amounts of reactants? 2Na(s)+Br2(g) ---->2NaBr(s) 1. 2mol Na, 2mol Br2 2. 1.8mol Na, 1.4mol Br2 3. 2.5mol Na, 1mol Br2 4. 12.6mol Na, 6.9 mol Br2
Wednesday, September 24, 2014 at 5:32pm
if 5.105 gm of KHP (Mwt=204.2)was dissolved in 250 ml,10.70 ml of this solution of KHP was titrated with 10.0 ml of NaOH . Calculate the concentration of NaOH solution
Wednesday, September 24, 2014 at 4:45pm
An alka-seltzer tablet weighing 3 grams is added to a flask of water (weighing 250 grams).At the end of the experiment, the flask weighs a total of 249.6 grams.Explain why this experiment does not seem to follow the Law of Conservation of Mass and how the experiment could be ...
Wednesday, September 24, 2014 at 4:21pm
The solubility of compound A in ethanol is 0.5 g per 100 mL at 0oC and 5.0 g per 100 mL at 78oC. (a) To make a hot, saturated solution of 15.0 g of A at 78oC, how much ethanol is required? (b) When the solution prepared in is cooled to 0oC, how much of compound A will be ...
Wednesday, September 24, 2014 at 12:21pm
How to determine direction of polarity? For instance im studying from a practice quiz, an it says that in CH3OH the oxygen is slightly negative, which is understandable as its next to F. but then it says the H is slightly positive. why the H and not the carbon which is two ...
Wednesday, September 24, 2014 at 11:53am
The solubility of acetanilide in your recrystallizing solvent is 5.0 mg per mL at 10 degrees Celsius. Calculate the maximum percent recovery in this experiment, assuming a 15.0 mL recrystallizing solution is filtered at 10 degrees Celsius.
Wednesday, September 24, 2014 at 5:38am
How can we prepare or change : 1) change unsaturated to saturated soln? 2) change unsaturated to supersaturated? 3) change saturated to unsaturated ? 4) change saturated to supersaturated ? 5) change supersaturated to unsaturated? 6) change supersaturated to saturated ?
Wednesday, September 24, 2014 at 3:13am
The solubility of LiCl is 83.5 g/100 g H2O at 20 oC , and is 89.8 g / 100 g H2O at 40 oC , then what is the required mass (in gram ) of LiCl to obtain a saturated solution in 300 g H2O at 25 oC ? please explain thank a lot
Wednesday, September 24, 2014 at 2:41am
Chemistry molar heat of fusion
A styrofoam cup with a mass of 2.97g has 81.68g of hot water at60.0 C has ice added to it untill it reaches a temrature of 7.0C and weights 141.12g. What is the molar heat lost by the water to melt the ice. Equation: -(mcdeltaT)=(deltaHn)+(mcdeltaT) m1=81.68g. ...
Wednesday, September 24, 2014 at 1:08am
Oops I left a part of the question out: 2. Mercury poisoning is a debilitating disease that is often fatal. In the human body, mercury reacts with essential enzymes, leading to irreversible inactivity of these enzymes. If the amount of mercury in a polluted lake is 215 ng of ...
Tuesday, September 23, 2014 at 10:26pm
Mercury poisoning is a debilitating disease that is often fatal. In the human body, mercury reacts with essential enzymes, leading to irreversible inactivity of these enzymes. If the amount of mercury in a polluted lake is 215 ng of mercury / mL, what is the total mass in ...
Tuesday, September 23, 2014 at 10:06pm
a vessel connected to an open-end mercury manometer is filled with gas to a pressure of .835 atm.the atmospheric pressure is 755 torr.In which arm of the manometer will the level of mercury be higher?What is the height difference between the two arms of manometer?
Tuesday, September 23, 2014 at 9:51pm
A professor orders 250 mL of house coffee at precisely 95°C. She then adds enough milk at 10°C to drop the temperature of the coffee to exactly 90° C. Calculate the amount of milk (in mL) the professor must add to reach this temperature. Assume that the coffee and ...
Tuesday, September 23, 2014 at 9:26pm
a) If the volume of a flask is 165 mL and the mass of the vapor in the flask is 0.2136 grams, what is the density of vapor in the flask? b)If the temperature of the vapor is 25 degrees Celsius, what is the molecular weight of the vapor? (Assume the gas pressure to be 1.00 atm.)
Tuesday, September 23, 2014 at 9:23pm
Chemistry, empirical formula
Determine the empirical formula for the following compounds with these compositions (by mass): a) Cr 47.7% F 52.3% b) Na 42.1% P 18.9% O 39.0%
Tuesday, September 23, 2014 at 9:19pm
A 50g chunk of metal (c=0.0506 j/g°C) is heated to 60°C. it is then dropped into a calorimeter(c=1.40 j/g°C,m=5.0 g)that contains 100.0g of an unknown liquid. the temperature of the liquid raises from 15°C to 20°C.What is the c of the calorimeter?
Tuesday, September 23, 2014 at 8:53pm
A sample of 1.15g of lead (II) nitrate is mixed with 121mL of 0.104 M sodium sulfate solution. Part A Write the chemical equation for the reaction that occurs.
Tuesday, September 23, 2014 at 5:57pm
10. A student weight out a 25 g sample of NaCl, SiO2 and NH4Cl. The student determines the sample contains 3.0 g NH4Cl and 7.0 g SiO2. What is the percentage of NaCl by mass (weight) in the sample?
Tuesday, September 23, 2014 at 5:08pm
Since a hydrogen atom consists of just one proton and one electron, it should have a mass of 1.673 x 10^-24 g. And so it does. Calculate how many hydrogen atoms you'd have if you had 5.6 g of hydrogen.
Tuesday, September 23, 2014 at 5:04pm
How much energy must you use to raise the temperature of 100 grams of water from 60 degrees Celsius to 70 degrees Celsius? show you calculations. I am confused on how to use formulas.
Tuesday, September 23, 2014 at 12:18pm
Analytical Chemistry (Titrations)
About 10ml of concentrated HCl was transferred to a 1-L volumetric flash and diluted to mark with distilled water. When this solution was used to titrate a sample of pure sodium carbonate, Na2Co3, weighing 0.3054 gram, it took 35.09 ml to reach the methyl red end point. The ...
Tuesday, September 23, 2014 at 12:15pm
Can someone tell me what steps i need to take? So confused on how to solve this An average human adult takes about 15breaths per min and exhales 23ml of co2 with each breath. If your trapped in a cave with pressure .963atm and 11C and your only source of oxygen is a breathing ...
Tuesday, September 23, 2014 at 11:40am
Suppose a metal worker shapes a 3.4 mg piece of gold until it is a thin, perfectly square plate that is uniformly 8.6x10^-6 cm thick. What is the length of a side of the plate, in cm?
Monday, September 22, 2014 at 11:00pm
I am having great difficulty with the following questions. Any and all help will be greatly appreciated. I have read the chapter and even looked up online tutorials. I still do not understand it. 2 NO (G) + O2 (G) > 2 NO2 (G) Write the equilibrium constant expression for ...
Monday, September 22, 2014 at 10:33pm
A 2.556g sample of baking soda (NaHCO3)decomposes to produce 0.876g of solid sodium carbonate. Caculate the theoretical yield and the percent yield of the sodium carbonate. The equation is: 2NaHCO3(s) -> Na2CO3(s) + H2O + CO2(g)
Monday, September 22, 2014 at 10:18pm
A graduated cylinder contains 56.3ml of water. A metal cylinder is dropped in the water and is completely covered by water. The diameter of the cylinder is 3.8 cm and the height of the cylinder in 5.4cm. What is the volume reading in the graduated cylinder after the cylinder ...
Monday, September 22, 2014 at 7:40pm
High School Chemistry
Determine the number of valence electron and the oxidation numbers for each of the following atoms. 1. Pb atomic #82 #valence e-'s= oxidation# =
Monday, September 22, 2014 at 5:44pm
4) Using your initial mass of copper (0.38), calculate the minimum volume of concentrated 12M nitric acid needed to completely react with your copper to form copper (II) nitrate 5) Using your answer from question 4 (2x10^-3 L), calculate the minimum volume of 6M sodium ...
Monday, September 22, 2014 at 5:26pm
Sorry to post this again, not sure if it was seen. If someone has the time to help with the following question it would be really helpful. Posted by Nancy on Monday, September 22, 2014 at 9:55am. The problem is 209/83bi+64/28NI=272/111Rg+1/0n How to calculate the energy change...
Monday, September 22, 2014 at 4:46pm
The problem si 209/83bi+64/28NI=272/111Rg+1/0n How to calculate the energy change in J/mol reactants? AMU amounts: Bi=208.980384 Ni= 63.927969 Rg=272.1535 What I have done is 1. subtract products from reactants. 2. multiply the result by 1.66054x10^-27kg 3. multiply that by 8....
Monday, September 22, 2014 at 9:55am
1 mole of nitroglycerin decomposes and release 5.72*10^3 KJ heat. to give CO2 H2O O2 and N2. A) write the balanced chemical equation B) calculate the work done assuming the temp of the reaction is 450K
Monday, September 22, 2014 at 12:42am
A 530 mL solution 10% HCl has been spilt onto the bench. It cannot be diluted or washed away. How much of the granular NaOH from the container seen in a previous photograph, must be used to neutralise the acid? [Using NaOH: MM = 40 g/mol]
Monday, September 22, 2014 at 12:38am