Explore BrainMass

# Stoichiometry

## BrainMass Solutions Available for Instant Download

### Density problem and pressure conversion problem

In determining the density of an unknown solid, it was immersed in water. If a portion of the sample sticks out the water, how will this effect the calculation of the density? Calculate the pressure of 756 mm Hg in the following units: a: atmospheres b. bar c. torr

### Carbonation and Solubility of Carbon Dioxide in Water

A miner working 260 m below sea level opened a carbonated soft drink during lunch break. To his surprise, the soft drink tasted rather "flat." Shortly afterward, the miner took an elevator to the surface. During the trip up, he could not stop belching. Why?

### Density and Standard Deviation

Water from cylinder to vial, the masses of water actually delievered for each of your 5 trials were: 9.848g, 9.957g, 9.918g and 9.773g Calculate the average volume of water dispensed and standard deviation. Assume the temperature of water is 25c and density is .99704 g/ml

### Why Barometer Readings Differ Around the World

Why is it that if the barometer reading falls in one part of the world, it must rise somewhere else? Explain your thinking and support your answer.

### Describe how the knowledge of the percent composition by mass of an unknown compound can help us identify the compound.

Describe how the knowledge of the percent composition by mass of an unknown compound can help us identify the compound.

### Mass Percentage of Dimercaprol

Dimercaprol (HSCH2CHSHCH2OH) is a complexing agent developed during world War I as an antidote to arsenic-based poison gas and used today to treat heavy-metal poisoning. Such an agent binds and removes the toxic element from the body. (a) If each molecule binds one arsenic (As) atom, how many atoms of As could be removed by 244

### Chemistry - Mass Ratio, Atoms and Density

When barium (Ba) reacts with sulfur (S) to form barium sulfide (BaS), each Ba atom reacts with an S atom. If 2.40 cm3 of Ba reacts with 1.65 cm3 of S, are there enough Ba atoms to react with the S atoms (d of Ba = 3.51 g/cm3; d of S = 2.07 g/cm3)? For barium sulfide, calculate the barium to sulfur mass ratio. From the in

### Converting parts per million to mg/kg

We have homework that says that 20.69 grams of material that has a % solids by weight of 1.84% is dissolved in 101.17 grams of HCl and then analyzed for zinc ---- the resultant zinc value of the dissolved solution in ppm is given as 65.33 ppm. I need to determine the mg/kg zinc as a function of only the the % solids in the or

### Electroplating : Mass of Copper and Silver on a Strip

Copper metal can reduce silver ions to metallic silver. The copper is oxidized to copper ions according to the reaction 2Ag^+(aq) + Cu(s) --> Cu^2+(aq) + 2Ag A copper strip with a mass of 2.00 g is dipped into a solution of AgNO3. After some time has elapsed, the copper strip is coated with silver. The st

### Wet Limestone Process : Calcium Carbonate and Calcium Sulfate

Assume that the wet limestone process requires 1 metric ton of calcium carbonate to remove +50.0% of the sulfur from 4 metric tons of coal containing +5.0% S. Assume that the sulfur product is calcium sulfate. Calculate the percentage of the limestone (calcium carbonate) converted to calcium sulfate.

### AgCl Solubility and Ksp

Suppose that a 20 mL sample of a solution is to be tested for the presence of chloride ion by the addition of 1 drop (.20 mL) 0.10M AgNO3. What is the minimum number of grams of chloride ion that must be present in order for AgCl to form?

### Unknown Concentrations from Chromatogram

3) Solution 1 contains a ratio of 2.54 :1 pentanol to hexanol. When the chromatogram was run, the peak area of the pentanol was found to be 4,320, and the peak area of the hexanol was found to be 4,156. When an unknown was run, a solution containing 1.00 mL of the unknown pentanol was mixed with 5 mL of 1.42 mM hexanol, and the

### Calculating Percent Yield

1.Sn(IV)4? -my experimental value was 0.194g and my melting point: 147 C - my balanced equation Sn + 2I2 -------> SnI4 - we used .24g of Sn, 0.95g I2 (I got 1.25 g as my theoretical value didn't look right so I need to double check) 2.Sn(II)I2? -my experimental value was 0.314g and melting point 160 C - balanced equa

### Wavelength and Absorbace

1. What is the wavelength of an emission line for iron that has a frequency of 5.68×1014 Hz? 2. A solution of CoL3+ has a percent transmittance of 28.9 % at 565 nm in a 2.00 cm cell. The molar absorptivity for the complex at this wavelength is 2.45×104 L/(mol?cm). What is the absorbance of CoL3+ in this solution? 3.

### Finding the Mass of a Plated Metal

Calculate how many grams of gold would be plated out on a coin, if a current of 2.3 (Amp) is applied for 15 min to an electrolytic cell shown above. The following reaction is occurring: Au^3+ + 3 e- &#8594; Au MW for gold equals 197g / mol. 1 amp (A) = 1 coulomb/second (C/s) Charge on 1 mol of electrons = 96500 coulombs

### A Beginner's Guide to Calculating Density

This posting provides a general definition of density as well as two example to calculate density. The first example is based on finding the density of a cube by calculating the cube's volume. The second example is based on finding the density of an egg using the volume displacement method.

### Reactions with Zinc Products

Find how many grams of zinc are produced when 500.00kJ of energy is evolved from the reaction of Cu II metal with zinc sulfide. (zinc blend) That should be balanced now. 2Cu + 2ZnS ---> 2CuS + 2Zn + 500.0 KJ Can someone give me advice or tell me what is not being understood. Full solution please.

### Application of Archimedes' Principle to Determine Density.

A student gently drops an object weighing 15.8g into an open vessel that is full of ethanol, so that a volume of ethanol spills out that is equal to the volume of the object. The experimenter then weighs the vessel and its contents and finds that it weighs 10.5g more than the vessel when it was full of ethanol only. The density

### Confirmation on Gas Pressures / Volume Problem (PV = nRT)

What is the pressure in atmospheres of 263 grams of N2 gas in a 10.0L container at 25.0oC. PV = nRT So: xV = nRT N2 = N(14.01) * 2 = 28.01 amu 263 / 28.01 = 9.3895037486611924312745448054266 moles of N2 gas x(10.0L) = 9.38950~(0.08206 * 25.0) x(10.0L) = 19.262566940378436272759728668331 x = 1.92625669403784362727597

### Molecular Weights and Percent of Element by Mass

1. Calculate the molecular weight of the following compounds: Al2(SO4)3 ____________________ SbBr5 ____________________ Fe(NO3)3 ____________________ C9H11NO2 ____________________ 2. Calculate the number of moles in 25 grams of each of the following compounds: C9H11NO2 ____________________ Al2(SO4)3 _________

### Precipitation Reaction: Mass of Ions Before Precipitation

A solution contains Cr3+ ion and Mg2+ ion. The addition of 1.00 L of 1.55 M NaF solution is required to cause the complete precipitation of these ions as CrF3 (s)and MgF2(s). The total mass of the precipitate is 50.2 g. Find the mass of the Cr3+ in the original solution.

### Calculation of moles of solute given molarity and volume of solute

How many grams of H3PO4 are in 265 mL of a 1.50M solution of H3PO4? This is a moles per liter and liters of solute type of problem which involves molecular weight calculated using the periodic table.

### Molecular Formula of a Gas

A gaseous hydrogen and carbon containing compound is decomposed and found to contain 85.63%C and 14.37%H by mass. The mass of 258 mL of the gas, measured at STP, was found to be 0.646 grams. What is the molecular formula of the compound?

### Mole percent of Helium-Oxygen Mixture

I am trying to figure out what percent (by moles) of He is present in a helium-oxygen mixture having a density of 0.528g/L at 25C and 721mmHg (torr).

### Reaction Balancing: Coefficient of H2O

1) Balance the equation below using the smallest set of whole numbers. What is the coefficient of H2O? ___PCl3(1)+ ___H2O(1) > ___H3PO3(aq)+ ___HCl(aq) 2)How many sodium atoms are there in 6.0g of Na3N

### Calculate the Mass from Moles

1) Calculate the molecular mass of potassium permanganate, KMnO4 2) What is the mass of 0.0250 mol of P2O5.

### Determining Number of Moles from mass

1) Determine the number of moles of aluminum in 96.7 g of Al. 2) How many moles are there in 8.0 g of ozone, O3.

### Limiting reagent amount estimation

Ammonia reacts with diatomic oxygen to form nitric oxide and water vapor: 4NH3 + 5O2 > 4NO + 6H2O When 20.0 g NH3 and 50.0 g O2 are allowed to react, which is the limiting reagent?

### Conversions and Dosage

Please see the attached file for the complete problems. Significant Figures in Calculations Part A Compute 3.5 * 4.48697 . Round the answer appropriately. Express your answer numerically using the proper number of significant figures. Part B Compute 1240.64/12.5. Round the answer appropriately. Express your answ

### Concentration of ion after precipitation

46.36 ml of 0.5000 M AgNO3 is added to 270.00 ml of water which contains 5.832g k2CrO4. A red precipitate of Ag2CrO4 forms. What is the concentration, in mol/L , of UNPRECIPITATED Cro4 2- ? Must have correct number of significant figures. Assume AgCrO4 is completely insoluble.