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Stoichiometry

Close packing in an FCC lattice

Potassium bromide, KBr, crystallizes like NaCl in a face centered cubic lattice. The ionic radius of K+ is 133 pm and the ionic radius of Br- is 195 pm. Assuming that all Br- ions are positioned in the face and corners of the unit cell, while the K+ ions are positioned along the edge alternating between anions, calculate the l

Ions

Calculate the total number of ions in 14.6 g CaH2.

Reaction - Fluorine Gas

Elemental sulfur occurs as octatomic molecules, S8. What mass of fluorine gas is needed for complete reaction with 218.48 g sulfur to form sulfur hexaflouride?

Volume Reading When Density is Given

The density of diamond is 3.51g/mL and the density of lead is 11.3g/mL. If equal masses of diamond and lead were transferred to equal volumes of water in seperate graduated cylinders, which graduated cylinder would have the highest volume reading? Explain your answer.

Purity and Density of metals

Determination of density has many practical applications. Is a piece of jewelry pure gold or is it an alloy perhaps of gold and silver? Give that the densities of gold and silver at 25 degrees C are 19.3 and 10.5g/mL respectively and that the volume of the alloy is the sum of the volumes of the metals used, calculate the density

Density

1) A material will float on the surface of a liquid if the material has a density of less than that of the liquid. Given density of water as 1.0g/mL, will a block having a volume of 1.2*10^4 in^3 and weighing 350 lb float or sink? 2) The density of pure silver is 10.5g/cm^3 at 20 degrees C. If 5.25 grams of pure silver pell

Significant figures and conversions

Please give rules for significant figures and explain as go along. 1) Put in decimal form and in scientific notation with sig. figures. a) 4.060 + 120.23 + 4.1*10^-2 b) (140) / [7.2*10^3 * 16.43 * (16.43 - 14.26)] 2) How many sig. figures? a) 100 b) 1.0*10^2 c) 1.00*10^3 d) 100. e) 0.0048 f) 0.00480 g) 4.8

Solutions

A solution of sodium cyanide (NaCN)is prepared by dissolving 50 grams into 500ml of solution. What is the Molarity,%(w/v), and ppm of the resulting solution.

The environmental protection agency (EPA) has proposed a new standard for microparticulates in air: a) how many of these particles are in your room? b)How many of these particles are in each 0.52-L breath you take?

The environmental protection agency (EPA) has proposed a new standard for microparticulates in air: For particles up to 2.5 um in diameter, the maximum allowable amount is 50 ug/m3. a) If your 9.2 ft x 13.8 ft x 8.6 ft dorm room just meets the new EPA standard, how many of these particles are in your room? (Assume the particle

Brackett Series

1) Lines in the Brackett series of the hydrogen spectrum are cause by emission of energry accompanying the fall of an electron from outer shells to the fourth shell. The lines can be calculated using the Balmer-Rydberg equation. See Attachement for equation where m = 4, R = 1.097 x 10-2nm-1 , and n is an integer greater th

Density

Nickels are composed of 25% nickel and 75% copper by mass, what is its density (d of nickel = 8.902 g/cm3; d of copper = 8.95 g/cm3)?

Particles

The environmental protection agency (EPA) has proposed a new standard for microparticulates in air: For particles up to 2.5 um in diameter, the maximum allowable amount is 50 ug/m3. If your 9.2 ft x 13.8 ft x 8.6 ft dorm room just meets the new EPA standard, how many of these particles are in your room? (Assume the particles are

Balanced Chemical Equations - Calcium Carbonate

136. What mass of calcium carbonate is required to react with the sulfur that is produced by burning 1000 kg of coal that contains 3.6 % sulfur by mass? Using a chemical equation convert the mass of coal to a mass of sulfur dioxide, then calculate the amount of calcium carbonate needed.

Molecular mass and moles

First, how many moles are present in each of the following masses? 2.58g of SrSO4 and 2.53 x10-3g of Ag2CO3. Second, going in reverse, How many grams are necessary to obtain the given number of moles? 3.20 x 10-4 moles of NaOH and 6.42 moles of AgNO3.

Hydroxide ion concentration using K or Kw not Ksp

At 25 degrees C, 0.212 g of barium hydroxide Ba(OH)2 (2 in lower position) is dissolved completely in sufficent water to make 0.25 litre final solution. What is the hydroxide ion concentration(in mol per litre) in this solution? Give the answer in scientific notation to an appropriate number of significant figures, and sta

Hydroxide ion concentration

At 25 degrees C, 0.212 g of barium hydroxide Ba(OH)2 is dissolved completely in sufficient water to make 0.25 litre final solution. What is the hydroxide ion concentration (in mol per litre) in this solution? Give the answer in scientific notation to an appropriate number of significant figures, and state the assumption you must

Working with Mole Fraction and Vapor Pressure

A solution of sodium chloride in water has a vapor pressure of 20.3 torr at 25°C. What is the mole fraction of NaCl in this solution.What would be the vapor pressure of this solution at 45°C? The vapor pressure of pure water is 23.8 torr at 25°C and 71.9 torr at 45°C

Osmotic pressure and molar mass

An aqueous solution of 10.00 g of an enzyme has a volume of 1.00 L at 29°C. The solution's osmotic pressure at 29°C is found to be 0.781 torr. Calculate the molar mass of the enzyme.

Mass percent and Molality Problem in Solutions

Assume that the density of water is 1.00 g/mL. % eth by volume = V of eth / (V of eth + V of water) * 100%. A bottle of wine contains 10.5% ethanol by volume. The density of ethanol (C2H5OH) is 0.789 g/cm3. Calculate the concentration of ethanol in wine in terms of mass percent and molality.

Mole Fraction and Conversions

What is the mole fraction of ethanol (C2H5OH) in a solution made by mixing a 20.0g sample of ethanol with 80.0g of water? What is the mole fraction of methanol (CH3OH) in a 92.5m aqueous solution? Please show all work and explain each step... It has been a while since I have taken chem and this is not my best subject.

Reactions and Moles

How many moles of water are made from the reaction of 2.2 moles of oxygen gas with unlimited quantities of hydrogen gas? Given the reaction:2H2 + O2 > 2H2O

Mass of Water through Vaporization

On january 1st of 2003 there were 50 kg of cucumbers in a vegetable store and they were 99% water by mass. On february 1st of 2003 they were 98% water, by mass due to loss of water through vaporization. What was the mass of cucumbers on February 1st of 2003?

Molarity of a solution

What is the molarity of a solution formed from 20.0 grams of NaCl dissolved in 650.0 mL of H2O?

Nickel Chloride and Sodium Phosphate Reaction

1. Nickel(11) chloride reacts with sodium phosphate to produce nickel(11) phosphate and sodium chloride. NiCl2(aq) + Na3PO4(aq) -----> Ni3(PO4)2 (s) + NaCl(aq) a. Balance the equation above b. Using the balanced equation, find out how many moles of nickel(11) chloride are required to produce 0.479 mol of nickel

Osmotic pressure problem

Brackish water with a salt content around .5 percent by mass is found in semiarid regions such as the American Southwest. Assuming that brackish water has the same density as pure water and contains only sodium chloride, estimate the osmotic pressure of brackish water at 298K. A hint is that the the total molarity is the sum

Antiprotons annihilate with protons

Compute the energy released in joules per event and in kilojoules per mole when antiprotons (the antimatter corresponding to protons) annihilate with protons. An antiproton has the same mass as a proton. Equation: 1 H + 1 H > energy

Empirical & Molecular Formula

When phosphorus is burnt in a free supply of air, diphosphorous pentoxide is formed. During later stages of combustion in a limited supply of air, the flame becomes larger greenish and flickering. Another phosphorus oxide is formed which is a white waxy crystalline solid which melts @ 23.8 degrees C and becomes a gas @ 176 degre