Practical Detection Questions and Answers

What mass of helium gas is needed to pressurize a 99.0L tank to 193 atm at 25 ⁰C? What mass of oxygen gas would be needed to pressurize a similar tank to the same Specifications?

A sample of glass was found on the prime suspect's shoe. Its mass was found to be 3.345 g and its volume was 1.50 mL. Where did this glass likely come from? Known Densities Standard auto glass 2.75 g/mL Pyrex pan found at the victim's house - 2.23 g/mL Broken window at victim's house-2.40 g/mL Broken drinking glass found at suspects house - 3.1 g/mL (a) the density of the glass found in the suspect's shoe matches the density of the broken glass found at their own home, the suspect likely stepped in glass at their own house (b) the density of the glass found in the suspect's shoe matches that of standard auto glass, the suspect likely stepped in some broken car window glass on the street (c) the density of the glass found in the suspect's shoe matches none of the known densities listed, the glass must have come from another source (d) the density of the glass found in the suspect's shoe matches the pyrex pan found at the victim's house, this is likely the source

A 3.50-g sample of a newly discovered metal from Mars absorbs heat, upon which the temperature of the sample increases from 20.0°C to 28.5 °C. The specific heat capacity of the metal is 0.68 Jg-1 K-1. How much heat was absorbed in J?

Which of the following correctly expresses the standard Gibbs free energy change of a reaction in terms of the reaction temperature (T) and equilibrium constant (K)? A) △G° = -RTInk B) △G° =eK/RT C) △G° = RTINK D) △G° = e^(-K/RT) E. None of above

Two elements A and B form compounds having formula AB2, and AB4, When dissolved in 20g of benzene (CH), Ig of AB, lowers the freezing point by 2.3 K whereas 1.0 g of AB, lowers it by 1.3K The molar depression constant for benzene is 5.1 K kg mol-. Calculate atomic masses of A and B.

When CO₂(g) reacts with H₂(g) according to the following reaction, 23.3 kJ of energy are absorbed for each mole of CO₂(g) that reacts. Complete the following thermochemical equation. 2CO₂(g) + 5H₂(g) ---> C₂H₂(g) + 4H₂O(g) ∆H =

At a certain temperature, calcium fluoride (CaF2) has a value of Ksp = 7.7 x10^-11. At this temperature, what is the molar solubility of CaF2 in the presence of 0.027 M Ca(NO3)2? Report your answer to two significant figures (i.e. 1.2E-5 M).

Decompression sickness is caused by Diving down too quickly when scuba diving Coming up too slowly when scuba diving Diving down too quickly when scuba diving Coming up too quickly when scuba diving

How much heat is needed to raise the temperature by 2.00°C for a metal with a specific heat of 0.780 J/g ºC and a mass of 45 grams?

According to Le Chatelier's principle, when the temperature of a system is reduced, the reaction will shift... (1) To the side with more gas molecules (2) To the side with fewer gas molecules (3) In favour of the exothermic reaction (4) In favour of the endothermic reaction

CuSO4(aq) + Zn(s) ---> + Cu(s) + ZnSO4(aq) The single-replacement reaction above produces 158.0 g of copper and an unknown concentration of zinc sulfate. With excess CuSO4, what mass of Zn was used? Molar mass of Cu: 63.55 g/mol ; Molar mass of Zn: 65.38 g/mol Answer: ________g of zinc (Use 4 sig figs)

What is the gram formula mass of Ca(OH)₂?

What is the total pressure of a methane-propane gas mixture if the partial pressure of methane is 655 torr and the partial pressure of propane is 280 torr? Enter your answer in torr to the nearest whole number, do not include units.

Use the reaction below to answer the question. PCI5 (g)⥨ PCl3 (g) + Cl₂(g) (△H=67kJ/mol) If the reaction is at equilibrium, and a scientist decreases the temperature of the reaction container, what will happen? The reaction will shift to the right More PCl3 will be produced More Cl₂ will be produced The amount of PCl5 will decrease. More PCl5 would be produced

Based on the half reactions below, which of the following chemical species is the strongest oxidant? Co²⁺(aq) + 2e‾ -> Co(s) E⁰ = -0.28 V vs SHE Pb²⁺(aq) + 2e‾ -> Pb(s) E⁰ = -0.13 V vs SHE a. Pb²⁺(aq) b. Co(s) c. Co²⁺(aq) d. Pb(s)

A stock solution was made by adding 200.0 g of CaCl₂ to 300.0 g of water. Next, a dilute solution is prepared by adding water to 16.50 mL of the stock solution to make the total mass of the solution equal to 98.00 g. What is the mass percent of CaCl₂ in the dilute solution?

A buffer solution is prepared with 0.371 M of benzoic acid , HC₇H₅O₂, and 0.186 M of sodium benzoate, NaC₇H₅O₂. For HC₇H₅O₂, Ka = 8.5 x 10‾⁵. What is the pH of this solution?

From experimental data, a student determined the concentration of acetic acid in vinegar to be 4.00%. If the true concentration of acetic acid is 8.00%, what is the percent error?

The solubility of CuSO₄ is 21.0 g per 100 mL of water at 20°C. At the same temperature, a certain solution contains 215 g of CuSO₄ dissolved in 1.0 L of water. What kind of solution is this? a. unsaturated solution b. saturated solution c. ultra unsaturated solution d. supersaturated solution

What is the percent by mass of Nitrogen in NH₄NO₃?

Which of the following is true about solubility? A. The solubility of most gas solutes decreases as the temperature of the solution decreases. B. The solubility of most solid solutes increases as the temperature of the solution decreases. C. The solubility of most gas solutes increases as the pressure increases. D. none of these

A gas cylinder contains O₂, nitrogen (220 mm Hg) and CO₂ (82 mm Hg). The total pressure in the cylinder is 625 mm Hg. The partial pressure of oxygen in this mixture is __________. a. 323 mm Hg b. 82 mm Hg c. 302 mm Hg d. 625 mm Hg

3. Iron (III) oxide, also known as rust can be removed from iron by reacting it with hydrochloric acid to produce iron (III) chloride and water. Fe203 (s) + 6HCI (aq) ---> 2FeCl3 + 3H₂0 (1) What mass of hydrogen chloride is required to react with 100 g of rust? a. 371g HCI b. 137g HCI c. 130g HCI d. 147g HCI

A balloon with a volume of 5.0 L is filled with a gas at 2 atmospheres. If the pressure is reduced to 1 atmospheres without a change in temperature, what would be the volume of the balloon? a. 5.0 L b. 10 L c. 12 L d. 10 ml

You invent a new unit system called the Blerg Unit System. The relationship between your unit system and other units are summarized below: 1 blah = 2.060 meters 1 blop = 3.05 pounds 1 kapow =11.8 liters You decide to convert all of your daily measurements to your new units. Assume you use 15.9 gallons of water when you shower. Convert this volume to kapows. [Hint: you may not need all of the above unit conversions.]

If the solubility of cholesterol in methanol were 1 g/100 mL at 20°C and 1 g/4.1 mL at 80°C, what is the maximum mass of cholesterol that could be recrystallized from 5.46 g cholesterol? Report the number of grams to two decimal places.

Experiment 14 Spectrophotometric Determination of an equilibrium constant, K₁. Based on the known concentration and absorption values the the Trendline from Beer-Lambert Law plot was, y = = 6455.4x -0.0175. Please answer the following questions. (a) for part i and ii please copy past from the following choices (Absorption, %T, Concertation of the complex ion) i. the y axis represents = ii. the x axis represents

What is the molarity of an calcium chlorate (Ca(CIO3)2) solution that has 0.17 moles dissolved in 875 mL? 1.2 M 0.194 M 1.94 x 10-4 M 1.33

Which of the following is true of a solution compared to the pure solvent? Solutions cannot exist in three phases but the pure solvent can. Solutions have a lower freezing point. Solutions have a higher vapor pressure, which means that evaporate more easily that the pure solvent. Solutions have a lower boiling point.

If you wanted to add 162 g of sodium carbonate (Na2CO3) to a prepare a 2.20 M solution, what volume, in liters, would you need?

6.00 M HCI was diluted to a 1.32 M solution. If there was 125 mL of the concentrated solution, what volume (in mL) of the dilute solution was made?

1). Without doing any calculations, determine whether the standard entropy change, AS is positive or negative for each of the following reactions. reaction 1: S(s, rhombic) + O2(g) → SO2(g) reaction 2: 2 SO₂(g)+ O₂(g) → 2 SO3(g) A) AS is positive for both reactions. B) AS is positive for reaction 1 but negative for reaction 2. C) AS is positive for reaction 2 but negative for reaction 1. D) AS is positive for both reactions.

After a certain reaction, it is determined that the total energy of the products is lower than the total energy of the original reactants. What happened with energy in the reaction? energy was created energy was destroyed energy was absorbed from the surroundings energy was released into the surroundings

Calcium Chloride is a salt that is commonly used to melt ice on roads when it snows. Assume that Calcium Chloride and Sodium Carbonate are the starting substances (reactants) in a reaction: physical states. Calcium ude the e. If 6.3 g of calcium chloride and 1.8 g of sodium carbonate are combined then theoretically, what mass of solid product could be formed from these amounts of reactants? What is the limiting reactant? f. What is the % yield if 3.550 g of the solid product was actually obtained?

Which of the following explains the increase of the reaction rate by a catalyst? The catalyst increases the number of collisions between the reactants molecules The catalyst decreases the rate of the backward reaction so that the rate of the forward reaction increases The catalyst provides an path of lowering activation energy to the reactants. None of the above

A gas is heated from 263K to 298K. The volume is increased from 24.0L to 35.0L. If the original pressure was 1.00 atm, what is the new pressure? 0.61 atm 1.28 atm 0.78 atm 1.65 atm

Using a table that lists standard heats of formation, you can calculate the change in enthalpy for a given chemical reaction. The change in enthalpy is equal to ________. Select one: a. ΔH, of products minus AHf of reactants b. ΔH, of products plus AH, of reactants c. ΔHf of reactants minus AHf of products d. ΔHf of products divided by AHf of reactants

N₂(g) + 3H₂(g) → 2NH3(g); ΔH = -91.8 kJ Consider the thermochemical equation for the synthesis of ammonia. Which statement is true? Select one: a. Negative enthalpy indicates that energy is required to complete the reaction. b. Negative enthalpy indicates a decrease in potential energy and an endothermic reaction. c. Enthalpy is negative indicating that energy is released so this is an exothermic reaction. d. Enthalpy is negative indicating that there is an energy deficit; the reaction is incomplete.

A landslide is a geological event caused by interactions between the four spheres. This landslide occurred after several weeks of steady rainfall. Explain how the landslide occurred in terms of potential energy and kinetic energy.

Jessica is doing her pre-lab homework for Chemistry. She is asked to predict how many grams of oxygen gas are produced if 40.0 g of potassium chlorate is decomposed according to this balanced chemical equation shown. 2KCIO3(s)-2KCI(s)+302(g) She performs the following calculation, and gets 15.7 g of O2 as her answer. The next day when her group performs the experiment they obtain an actual yield of 14.5 grams of oxygen gas. What is the percent yield for the experiment? report your answer to the tenths place, i.e. one decimal place.

A student conducted an experiment and combined sodium chloride with magnesium hydroxide to produce sodium hydroxide and magnesium chloride. The student collected the 120 grams of NaOH. How many moles of NaOH were formed in the experiment? 160 3.0 4800 0.33

Samuel is applying to three different law schools. (main) They are all located in California. (adj) Samuel is applying to three different law schools who are all located in California. Samuel who is applying to three different law schools which are all located in California. Samuel is applying to three different law schools that are all located in California. Samuel who are all located in California is applying to three different law schools.

According to collision theory, in order for two molecules to bond they must collide with each other. The collision must also have enough energy and hit with the proper orientation. Which of these will increase the rate of a chemical reaction? Select one: a. Increasing the size of the container holding the substances. b. Decreasing the temperature of the substances that are reacting. c. Increasing the amount of the substances to the reaction chamber. d. Decreasing the pressure on the substances in the reaction chamber.

"A Poison Tree" By William Blake I was angry with my friend; I told my wrath, my wrath did end. I was angry with my foe: I told it not, my wrath did grow. And I watered it in fears, Night & morning with my tears: And I sunned it with smiles, And with soft deceitful wiles. And it grew both day and night. Till it bore an apple bright. And my foe beheld it shine, And he knew that it was mine. And into my garden stole, When the night had veild the pole;

Given the reaction: Show all your work 3 A (aq) + B (1) 2 C (aq) + 2 D (aq) a) What is the expression for the equilibrium constant? (1 point) b) Using your equation from above, what is the value of the equilibrium constant if at equilibrium [A] is 0.3 M, and both [C] and [D] is 0.00061 M ? (3 points)

Given the equation below, how many grams of H₂O would be formed when 64.79 grams of H3PO4 is reacted with excess CuO? Remember to round your answer to the nearest 0.01 and include both units (properly abbreviated) and substance formula in your answer. 3 CuO + 2 H3PO4 --> Cu3(PO4)2 + 3 H₂O

What do the SI prefixes giga and micro represent, respectively (order same as listed)? A. 109 and 10-6 B. 10-⁹ and 10-6 C. 106 and 10⁹ D. 10-6 and 10⁹ E. 109 and 106

Consider the hypothetical atom "X". If the molecular formula for sodium carbonate is Na₂CO3 and the formula of "X" oxide is X203. What is the molecular formula for "X" carbonate? A. X₂(CO3)3 B. X3CO3 C. X3(CO3)2 D. X(CO3)2 E. XCO3

Chlorobenzene, C6H5Cl, is used in the production of chemicals such as aspirin and dyes. One way that chlorobenzene is prepared is by reacting benzene, C6H6, with chlorine gas according to the following BALANCED equation. C6H6 (l) + Cl₂ (g) --------- 6H5Cl (s) + HCl (g) 12.01 X 6 a. If the theoretical yield for C6H5Cl is 65.2 g and the actual yield is 63.7 g, what is the percent yield? Insert photo of work here:

The equilibrium constant for the following reaction is 650 at 298K. CH3OH(l) CO(g) + 2H₂(g) The value of ΔG for this reaction is _______ kJ/mol A) 0 B) some number less than zero C) some number greater than zero D) Equal to K