Sunday
March 9, 2014

# Homework Help: Science: Chemistry

Chemistry
No but it isn't Ca and Al. Note it is Ca and Al^3+ ION
Tuesday, October 22, 2013 at 10:13pm

Chemistry
not quite. FeO + O2 ==> Fe2O3 For iron(II) oxide. you're told Fe is +2 and you know O is -2; therefore, the formula must be FeO For iron(III) oxide, iron is +3 and O is -2; therefore the formula is Fe2O3.
Tuesday, October 22, 2013 at 10:10pm

Chemistry
Ba(OH)2 + 2HCl ==> BaCl2 + 2H2O or 2OH^- + 2H^+ ==> 2H2O You added 0.02145 mol OH^- to 0.0429 mols H^+ to produce 0.02145 mol H2O. q = mass H2O x specific heat H2O x (Tfinal-Tinitial) Substitute and solve for q. That gives you q for 0.0215 mols reacted or q/0.02145 = ...
Tuesday, October 22, 2013 at 10:06pm

ap chemistry
Using 12.011 for atomic mass C I obtained 20,666,000 J. 1. Did you substitute -20665.3 kJ convert to J. If so that's the problem. That is a + number when you heat the water. 2. If you used a + number then count the number of significant figures. That's often a problem ...
Tuesday, October 22, 2013 at 9:44pm

Chemistry
How many atoms of nitrogen are in the same amount of ammonia? Use molar mass.
Tuesday, October 22, 2013 at 9:42pm

chemistry
What mass of magnesium chloride is formed in the reaction between 7 g of Mg and 7.9 g of Cl2
Tuesday, October 22, 2013 at 9:39pm

ap chemistry
q = [mass H2O x specific heat H2O x (Tfinal-Tinitial)] + [Ccal x (Tfinal-Tinitial)] Then delta E/g = q/0.515 g delta E/mol = delta E/g x (56.0 g/mol)
Tuesday, October 22, 2013 at 9:27pm

chemistry
if 5.2 grams of bismuth react under certain conditions with 10.0 g of oxygen what is the empirical formula of the bismuth formed
Tuesday, October 22, 2013 at 9:26pm

ap chemistry
See you post on steam to ice.
Tuesday, October 22, 2013 at 9:23pm

Chemistry
I believe this is E2-E1 = delta E = q+w dE = 7495 w is -346 q = 7495+346 = ? Then q = mass gas x specific heat gas x (Tfinal-Tinitial) Solve for specific heat gas.
Tuesday, October 22, 2013 at 9:21pm

ap chemistry
For the first question, the answer I got was -20665.3 kJ and it was correct. However, every time I plug that answer into the equation I get the wrong answer for the second question. I've converted the aforementioned number into joules but I still got the wrong answer when ...
Tuesday, October 22, 2013 at 9:17pm

Chemistry
80%
Tuesday, October 22, 2013 at 9:02pm

ap chemistry
q = mass H2O x specific heat H2O x (Tfinal-Tinitial). would convert q in J to q in kJ. delta H soln in kJ/g = q from above/1.67g delta H soln in kJ/mol = kJ/g x (146 g/1 mol) = ?
Tuesday, October 22, 2013 at 8:48pm

ap chemistry
Tuesday, October 22, 2013 at 8:44pm

ap chemistry
An easy but long problem. You have two formulas to use for this. Within a phase (all gas, all liquid, all solid), q = mass x specific heat x (Tfinal-Tinitial) At a transition point: At the boiling point is is q = mass x heat vaporization At the melting point it is q = mass x ...
Tuesday, October 22, 2013 at 8:43pm

ap chemistry
q1 = heat to raise T from 19 C to 961 C. q1 = mass Ag x specific heat Ag x (Tfinal-Tnitial) q2 = heat to melt Ag. q2 = mass Ag x heat fusion Total q = q1 + q2
Tuesday, October 22, 2013 at 8:38pm

ap chemistry
394 kJ x (630/12) = ? q = mass H2O x specific heat H2O x (Tfinal-Tinitial) Substitute and solve for mass H2O. Remember to use q in J not kJ.
Tuesday, October 22, 2013 at 8:35pm

Chemistry- DrBob222
All of your work looks good to me.
Tuesday, October 22, 2013 at 8:30pm

CHEMISTRY
Didn't I answer this for you last night?
Tuesday, October 22, 2013 at 8:25pm

CHEMISTRY
Why dont you post all questions first, not many of use have the time to wait around to pay attention to your followon posts.
Tuesday, October 22, 2013 at 8:24pm

CHEMISTRY
What volume of 0.400 M Hg(NO3)2 is needed to precipitate all the I- ions from 250.0 mL of 0.300 M FeI3 There will be a follow-up questions so pay attention to my post!
Tuesday, October 22, 2013 at 8:22pm

Chemistry
45
Tuesday, October 22, 2013 at 6:54pm

Chemistry- DrBob222
I completed this question like you told me to. Are the answers correct? Is my method for finding the molecular formula correct? 2.4g of a compound of carbon, hydrogen and oxygen gave on combustion, 3.52g of CO2 and 1.44g of H2O. The relative molecular mass of the compound was ...
Tuesday, October 22, 2013 at 6:50pm

ap chemistry
Suppose that coal of density 1.5 g/cm3 is pure carbon. (It is, in fact, much more complicated, but this is a reasonable first approximation.) The combustion of carbon is described by the equation C(s) + O2(g) −! CO2(g) H◦ = −394 kJ What is the value of q...
Tuesday, October 22, 2013 at 6:28pm

ap chemistry
How much heat is required to heat 19 g of solid silver from 100 ◦C to liquid silver at 961◦C? The specific heat of solid silver is 0.235 J/g ·◦ C, and the heat of fusion of silver at its melting point of 961◦C is 11.3 kJ/g. Answer in units of kJ
Tuesday, October 22, 2013 at 6:25pm

ap chemistry
Consider the specific heats CH2O(s) = 2.09 J/g ¡¤◦ C. CH2O(§¤) =4.18 J/g ¡¤◦ C. CH2O(g) = 2.03 J/g ¡¤◦ C. The heat of fusion for water is 334 J/g and the heat of vaporization for water is 2260 J/g. Calculate ...
Tuesday, October 22, 2013 at 6:23pm

ap chemistry
Consider the specific heats H2O(s) =2.09 J/g ¡¤◦C,H2O (§¤) = 4.18 J/g ¡¤◦C, and H2O(g) = 2.03 J/g ¡¤◦C. The heat of fusion for water is 334 J/g and its heat of vaporization is 2260 J/g. Calculate the amount ...
Tuesday, October 22, 2013 at 6:20pm

ap chemistry
When 0.515 g of compound X is burned completely in a bomb calorimeter containing 3000 g of water, a temperature rise of 0.243◦C is observed. What is Urxn for the combustion of compound X? The hardware component of the calorimeter has a heat capacity of 3.12kJ/◦...
Tuesday, October 22, 2013 at 6:18pm

ap chemistry
A sample of 1.67 grams of Z is dissolved into 500 grams of water which is in a Styrofoam coffee cup. The temperature is monitored and is found to rise from 25.594◦C to 26.041◦C. What is Hsolution for substance Z? Assume no heat is lost/gained by the cup itself...
Tuesday, October 22, 2013 at 6:17pm

Chemistry
An 80.0 g sample of a gas was heated from 25 degree C to 225 degree C. During this process, 346 J of work was done by the system and its internal energy increased by 7495 J. What is the specific heat of the gas? J/(g∗C)
Tuesday, October 22, 2013 at 6:16pm

ap chemistry
Calculate the energy required to heat 827 g of mercury from 37 ◦C to 42 ◦C. The specific heat capacity of Hg(§¤) is 0.138 J/g ¡¤◦ C. Answer in units of calories
Tuesday, October 22, 2013 at 6:13pm

Chemistry
In a constant-pressure calorimeter, 65.0 mL of 0.330 M Ba(OH)2 was added to 65.0 mL of 0.660 M HCl. The reaction caused the temperature of the solution to rise from 23.85 °C to 28.35 °C. If the solution has the same density and specific heat as water, what is ΔH ...
Tuesday, October 22, 2013 at 6:13pm

CHEMISTRY HELP
nya
Tuesday, October 22, 2013 at 6:09pm

Chemistry
If you have iron(II) oxide(s) + oxygen(g) ---> Iron(III) oxide(s), Would the answer be FeO3 + O2 ---> FeO3 for a skeleton equation?
Tuesday, October 22, 2013 at 4:32pm

Chemistry
You need to be more specific here. I can't tell from what you've written what you are doing or what you are asking.
Tuesday, October 22, 2013 at 3:19pm

Chemistry
Make sure the water’s Mass is still set to 1.0 kg and its Temp is 25 °C. Set the cylinder’s Height to 500 m. How does doubling the mass affect the temperature change of the water?
Tuesday, October 22, 2013 at 2:46pm

Chemistry
E = hc/wavelength Remember h is Planck's constant c is speed of light in m/s wavelength must be in m Solve for E in J and this is for 1 photon. Multiply by 6.02E23 to obtain J/mol and convert to kJ. Do this for 230 nm and 290 nm and I would quote the range in energy.
Tuesday, October 22, 2013 at 2:26pm

Chemistry
[Ccal x (Tfinal-Tinitia)] + [mass Cal H2O x specific heat H2O x (Tfinal-Tinitial)] + [mass warm H2O x specific heat H2O x (Tfinal-Tinitial)] = 0 Substitute and solve for Ccal.
Tuesday, October 22, 2013 at 2:23pm

Chemistry
A calorimeter contains 50.0 mL of water; both are at 21.2 degrees C. Then the 50.0 mL of water at 57.6 degrees C is added to the calorimeter. At equilibrium, the final temperature of the water and the calorimeter is 33.3 degrees C. Calculate the heat capacity, C, of the ...
Tuesday, October 22, 2013 at 12:04pm

Chemistry
The protective action of ozone in the atmosphere comes through ozone's absorption of UV radiation in the 230 to 290 nm wavelength range. What is the energy, in kilojoules per mole, associated with radiation in the wavelength range?
Tuesday, October 22, 2013 at 11:41am

chemistry
15 cal/C
Tuesday, October 22, 2013 at 3:08am

chemistry 101
15 cal/C
Tuesday, October 22, 2013 at 3:08am

Chemistry
A/sec x (60 min/sec) = ?
Tuesday, October 22, 2013 at 1:30am

Chemistry
Thanks. I agree.
Tuesday, October 22, 2013 at 1:15am

college chemistry
exactly 11.2 ml of water at 23°c are added to a hot iron skillet. all of the water is converted into steam at 100°c. the mass of the pan is 1.5 kg and the molar heat capacity of iron is 25.19 j/(m·°c). what is the temperature change of the skillet
Tuesday, October 22, 2013 at 1:14am

Chemistry
Help! If I have 0.0031 absorbance/sec, how would I convert this to absorbance/minute? Thanks
Tuesday, October 22, 2013 at 1:06am

chemistry
256 Hz. If you want to get confused read this site about "scientific pitch notation" and 261.6 Hz for middle C. http://en.wikipedia.org/wiki/C_%28musica​l_note%29
Tuesday, October 22, 2013 at 12:58am

Chemistry
Oh, ok well i came out with a pH of 5.22. pH = pKa + log A/HA. I came up with .15M as A and .05 as HA. So 4.74+log(3)= 5.22.
Tuesday, October 22, 2013 at 12:56am

Chemistry...
I don't think so. Hg^2+ + 2I^- ==> HgI2 mols I^- = M x L x 3 = 0.225 So you need 1/2 that mols Hg^2+. M = mols/L or L = mols/M 0.1125/0.400 = 0.281L.
Tuesday, October 22, 2013 at 12:47am

Chemistry
Why don't you show what you have and how you obtained that and let US check you?
Tuesday, October 22, 2013 at 12:37am

Chemistry
It may mean oxidation or further reaction with one of the precipitating agents.
Tuesday, October 22, 2013 at 12:36am

Chemistry
What does a change in the color of precipitate over time when a mixture of two solutions is combined with a reagent indicate?
Tuesday, October 22, 2013 at 12:23am

Chemistry
what is the resultig pH if 0.005 mol of NaOH is added to 100.0mL of buffer containing 0.010 mol acetic acid (CH3COOH,pKa = 4.74)and 0.010 mol sodium acetate (NaCH3COO)? (Assume the final volume is 100 mL) So i worked it out, i just need to double check the pH. Let me know what...
Tuesday, October 22, 2013 at 12:05am

Chemistry...
What volume of 0.400 M Hg(NO3)2 is needed to precipitate all the I- ions from 250.0 mL of 0.300 M FeI3? Is the answer 93.8mL??
Tuesday, October 22, 2013 at 12:02am

chemistry
A tuning fork produces a sound of musical note middle C. It moves back and forth 256 time each second. what is the frequency of the tuning fork?
Monday, October 21, 2013 at 11:53pm

chemistry
a tuning fork produces a sound of musical note middle C. It moves back and forth 256 time each second. What is the frequency of the tuning fork?
Monday, October 21, 2013 at 10:06pm

Chemistry
Thanks, but for the first one, I thought it'd be no reaction since they are both metals. Is it possible for Ca and Al to react with each other?
Monday, October 21, 2013 at 9:17pm

CHEMISTRY
Monday, October 21, 2013 at 8:22pm

CHEMISTRY
Monday, October 21, 2013 at 8:21pm

CHEMISTRY
What units do you want this. This often is reported in mg/L. 0.4078g PbCO3 x (molar mass Pb^2+/molar mass PbCO3) = ?g Pb and convert that to mg. That is mg/100 mL, convert to mg/L. Pb^2+ =
Monday, October 21, 2013 at 8:21pm

Chemistry
Monday, October 21, 2013 at 8:15pm

Chemistry
First you must recognize that you can't crumple these things up and place them in a one box fits all. Some reactions may be more than one type. 2Na + 2H2O ==> H2 + 2NaOH This is a redox rxn, a single replacement, and by some schemes even an acid/base rxn. 1. redox 2. ...
Monday, October 21, 2013 at 8:15pm

Chemistry
n1 = 2; n1^2 = 4 n2 = 3; n2^2 = 9 E = 2.179E-18(1/4-1/9) Solve for E, then E = hf and solve for f.
Monday, October 21, 2013 at 8:07pm

chemistry
Write the name of $${\rm CrPO}_{4}$$
Monday, October 21, 2013 at 7:52pm

chemistry
First separate the reaction into reduction and oxidation reactions. Then add the right number of electrons to balance the charges. Reduction: Mn(2+) -> Mn(5+) Mn(2+) -> Mn(5+) + 3e- Oxidation: Sn(2+) -> Sn Sn(2+) + 2e- -> Sn And then balance both reactions such ...
Monday, October 21, 2013 at 7:24pm

chemistry
balance the following ionic equation: Sn(2+)(aq)+ Mn(2+)(aq)----- Mn(5+)(aq)+ Sn (s)
Monday, October 21, 2013 at 7:09pm

Chemistry
The energy (in joules) of an electron energy level in the Bohr atom is given by the expression: En = -2.179E-18/n2 J where n is the quantum number that specifies the energy level. What is the frequency in Hz of the radiation emitted when an electron falls from level n = 3 to ...
Monday, October 21, 2013 at 7:05pm

Chemistry
What kind of reaction is this (redox, precipitation, acid-base, or complex ion formation reaction)? 1. 3 Ca(s) + 2 Al^3+(aq) -> 3 Ca^2+(aq) + 2 Al(s) 2. LiHCO3(s) + heat -> Li2CO3(s) + CO2(g) + H2O(g) Complete the reaction: Ni(s) + 2 Na^+(aq) -> ?
Monday, October 21, 2013 at 7:04pm

Chemistry
The energy (in joules) of an electron energy level in the Bohr atom is given by the expression: En = -2.179 x 10-18/n2 J where n is the principal quantum number for the energy level. What is the frequency in Hz of the electromagnetic radiation absorbed when an electron is ...
Monday, October 21, 2013 at 7:00pm

chemistry
When a photon of light hits the surface of a metal, a photoelectron may be emitted. Some of the photon's energy is required to free the electron from the surface. The remaining energy becomes the kinetic energy of the photoelectron. The minimum energy for the emission of ...
Monday, October 21, 2013 at 6:59pm

Organic Chemistry
Both benzoic acid and triphenyl are organic solutes, and therefore will dissolve in organic solvents. (ie: diethyl ether) Benzoic acid (an acid) will react with a strong base (ie: NaOH) to form sodium benzoate (which is a water soluble salt) and aqueous NaCl. Therefore, if you...
Monday, October 21, 2013 at 6:08pm

Chemistry
When 1.00 kg lead (specific heat = 0.13 J g -1 C -) at 100.0 C is added to a quantity of water at 28.5C, the final temperature of the lead-water mixture is 35.2 C. What is the mass of water present?
Monday, October 21, 2013 at 4:39pm

Chemistry-correction
*sorry, my conversion of 2.5 kg to g is wrong. The equation should be Q = (2500 / 200.6)*(28.0)*(-6 -(-20))
Monday, October 21, 2013 at 4:25pm

CHEMISTRY
The concentration of Pb2+ in a sample of wastewater is to be determined by using gravimetric analysis. To a 100.0-mL sample of the wastewater is added an excess of sodium carbonate, forming the insoluble lead (II) carbonate (267.2092 g/mol) according to the balanced equation ...
Monday, October 21, 2013 at 4:21pm

CHEMISTRY
The concentration of Pb2+ in a sample of wastewater is to be determined by using gravimetric analysis. To a 100.0-mL sample of the wastewater is added an excess of sodium carbonate, forming the insoluble lead (II) carbonate (267.2092 g/mol) according to the balanced equation ...
Monday, October 21, 2013 at 4:21pm

Chemistry
Through out the temperature range, Hg remains as liquid. Recall that heat released or absorbed is given by Q = m*c*(T2 - T1) where m = mass c = specific heat T = temperature Note that molar mass of Hg is 200.6 g/mol. Substituting, Q = (250000 / 200.6)*(28.0)*(-6 -(-20)) Q = ? ...
Monday, October 21, 2013 at 4:18pm

CHEMISTRY
The concentration of Pb2+ in a sample of wastewater is to be determined by using gravimetric analysis. To a 100.0-mL sample of the wastewater is added an excess of sodium carbonate, forming the insoluble lead (II) carbonate (267.2092 g/mol) according to the balanced equation ...
Monday, October 21, 2013 at 4:16pm

Chemistry
How much heat, in kilojoules (kJ), is required to raise the temperature of 2.50kg Hg(l) from -20.0 to -6.0C? Assume a density of 13.6g/ml and a molar heat capacity of 28.0 J mol -1 C -1 for Hg(l). Please helpppppp .... thanks in advance
Monday, October 21, 2013 at 4:05pm

chemistry
How about Al(NO3)3+ 3NaCl = AlCl3 + 3NaNO3
Monday, October 21, 2013 at 3:31pm

chemistry
Al(NO3)3+ NaCl
Monday, October 21, 2013 at 3:24pm

Science, Chemistry
A cylinder containing 11.0L of helium gas at a pressure of 165atm is to be used to fill birthday balloons to a volume of 2.50L per balloon and at a pressure of 1.10atm. What is the maximum number of balloons that can be inflated at a constant temperature? (remember that 11.0L ...
Monday, October 21, 2013 at 2:48pm

Chemistry
What you outlined is ok and that will work for the theoretical percent KClO3 but as soon as you find n and convert to mass O2 I assume that is not a volume percent anymore but a mass percent. So I avoided that route and stuck with volume.
Monday, October 21, 2013 at 2:37pm

chem 1211
This is a limiting reagent problem. Here is a step by step procedure for working a limiting reagent problem. http://www.jiskha.com/science/chemistry/​limiting_reagent_problem.html
Monday, October 21, 2013 at 2:33pm

chemistry
oxidation of 1,methyl-propanone with the presence of KMnO4 & conc H2SO4 under heat.
Monday, October 21, 2013 at 11:37am

chemistry
It's an exothermic reaction, since heat is released.
Monday, October 21, 2013 at 10:26am

chemistry
n an experiment, Ann mixes concentrated sulfuric acid with water in a reaction test tube. The walls of the test tube turn hot. What type of reaction has occurred?
Monday, October 21, 2013 at 10:19am

chemistry
If 2.0 Grams of anhydrous sodium sulfate are mixed with 2.0 grams of calcium chloride dihydrate and 2.0 grams of calcium sulfate dihydrate are collected, what is the percent yield?
Monday, October 21, 2013 at 1:51am

chemistry
If 2.0 Grams of anhydrous sodium sulfate are mixed with 2.0 grams of calcium chloride dihydrate and 2.0 grams of calcium sulfate dihydrate are collected, what is the percent yield? DO NOT ROUND A NUMBER IF USED IN A SUBSEQUENT CALCULATION
Monday, October 21, 2013 at 1:40am

Chemistry
Thanks for replying. No, this isn't a pure sample of KClO3. The mixture is 90% KClO3 and 10% MnO4 (catalyst) for the decomposition of KClO3. I understood most of what you said but you lost me at the part where you talked about using the gram sample and converting it to ...
Monday, October 21, 2013 at 1:06am

Chemistry
I came up with 12.0556 which I would round to 12.056 and that's too many significant figures. By the way, I don't see but two isotopes for B; i.e., B-10 and B11. This may be a made up problem. See http://www.webelements.com/boron/isotope​s.html
Monday, October 21, 2013 at 12:45am

chemistry
fart
Monday, October 21, 2013 at 12:32am

Chemistry
Is this a pure sample of KClO3 or a sample given to you that is KClO3 + some inert material? -Mass of glassware: 120.3340g -Mass of glassware+sample (Before heat)= 122.3240g mass KClO3 sample = 122.3240-120.3340 = ?g -Mass of Glassware+sample (After heat)= 121.6070g mass O2 = ...
Monday, October 21, 2013 at 12:30am

Chemistry
Would the correct answer be 12.167?
Sunday, October 20, 2013 at 11:55pm

Chemistry
Hi, I'm doing a chem lab of the Percent Composition of Potassium Chlorate-A Gas Law Experiment and we need to calculate the percent of KClO3 in the sample volumetrically and gravimetrically. I need help calculating the Volumetric percent of KClO3 in sample given the ...
Sunday, October 20, 2013 at 11:43pm

Chemistry
So the third isotope has an abundance of 100%-54.4%-12.75% = ? = about 32.85% or 0.3285 as a decimal). If we let Z = atomic mass of the third isotope we have\ 10.0129(0.544) + 11.0093(0.1275) + Z(0.3285) = 10.811 Solve for Z.
Sunday, October 20, 2013 at 11:37pm

Organic Chemistry lab
Sunday, October 20, 2013 at 11:31pm

Organic Chemistry
NaHCO3 is used to get rid of the excess HCl used in the experiment. You don't use NaOH because t-pentyl chloride + NaOH ==> the alcohol so you undo what you've done.
Sunday, October 20, 2013 at 11:30pm

Chemistry
The element boron has three naturally occuring isotopes. One has the atomic mass 10.0129(54.4%), another 11.0093(12.75%). What is the atomic mass of the third isotope if the average atomic mass of boron is 10.811?
Sunday, October 20, 2013 at 11:27pm

Chemistry
THANK YOU!!!!
Sunday, October 20, 2013 at 11:26pm

CHEMISTRY
25cm^3 of a solution of NaOH required 28cm^3 of 1.0 mol dm^-3 H2SO4 to neutralise it. a)Write an equation for the reaction. 2NaOH + H2SO4 ==> Na2SO4 + 2H2O b)How many moles of H2SO4 were needed? mols H2SO4 = M x L = ? c)How many moles of NaOH were thus neutralised? ?mol ...
Sunday, October 20, 2013 at 11:19pm

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