Practical Detection Questions and Answers

to access important values if needed for this Using average bond enthalpies linked above estimate the enthalpy change for the following reaction 2HBr g Cl g 2HCl g Br g

A piece of plastic has a thickness of 4 70 x 10 um Express this in meters nanometers and picometers nm pm

A chemist prepares a solution of Iron III bromide FeBr by measuring out 64 umol of iron III bromide into a 50 mL volumetric flask and filling the flask to the mark with water Calculate the concentration in mol L of the chemist s iron III bromide solution Round your answer to 2 significant digits M mol

A compound is found to contain 37 47 carbon 12 61 hydrogen and 49 92 oxygen by mass To answer the question enter the elements in the order presented above QUESTION 1 The empirical formula for this compound is QUESTION 2 The molar mass for this compound is 32 05 g mol The molecular formula for this compound is

0 Sample Furnace empirical formula H O absorber When 4 717 grams of a hydrocarbon CxHy were burned in a combustion analysis apparatus 14 80 grams of CO2 and 6 060 grams of H O were produced In a separate experiment the molar mass of the compound was found to be 28 05 g mol Determine the empirical formula and the molecular formula of the hydrocarbon Enter the elements in the order presented in the question molecular formula CO absorber

The percent by mass of aluminum in Al NO2 3 is

For the following reaction 4 29 grams of sulfur are mixed with excess carbon monoxide The reaction yields 7 29 grams of sulfur dioxide sulfur s carbon monoxide g sulfur dioxide g carbon s What is the theoretical yield of sulfur dioxide What is the percent yield of sulfur dioxide grams

Write out steps to show how each of the following pairs of compounds can be separated by an extraction procedure a b NH N HO and and

values if needed for this question How many moles of bromine trifluoride are needed to produce 8 74 L of fluorine gas according to the following reaction at 0 C and 1 atm bromine trifluoride g bromine g fluorine g moles bromine trifluoride

A chemical reaction is run in which 389 Joules of heat are generated and 684 Joules of work are done on the system Calculate the change in the internal energy of the chemical system AU Joules

Write the chemical formula of the following metal complexes or complex ions formula 0 EX name tetracyanocobaltate III dibromobis ethylenediamine zinc II

A 1 21 mol sample of CO2 gas is confined in a 30 1 liter container at 30 4 C If the temperature of the gas sample is increased to 52 1 C holding the volume constant the pressure will increase because Choose all that apply At higher temperatures molecules have higher average speeds With lower average speeds the molecules hit the walls of the container less often With higher average speeds on average the molecules hit the walls of the container with more force As the average speed increases the number of molecule wall collisions decreases

to access important values if needed for this question ixture of argon and hydrogen gases in a 8 40 L flask at 48 C contains 9 93 grams of argon and 0 528 grams of hydrogen The partial pressure of hydrogen in the flask is atm and the total pressure in the flask is atm

A cell with a total of 0 2 osmol L is placed into a solution with a total of 0 3 osmol L switched from the previous question It is assumed that the osmotic particles cannot pass through the cell membrane Answer the following true or false questions a true b false Solvent is more concentrated in the cell Water will osmose out of the cell The cell will shrink and may look crenated Plant cells have a cell wall to protect them from dehydration caused by osmosis

2Mg s O g 2MgO s A college chemistry student is performing this reaction in a lab where magnesium is burned and combines with oxygen from the air to produce magnesium oxide The students burns 2 92 g of Mg and there is excess oxygen from the air They incorrectly calculated that the mass of magnesium oxide produced was 2 42 g Here is their work 2 92 g 40 3 g 24 3 g 1 mol 1 mol 2 mol X X 1 mol X 2 42 g 1 What did the student do wrong There is an error in their work Explain specifically what part is incorrect 2 pts 2 What recommendation s would you give to the student regarding showing their work There is an improvement that can be made to help them avoid this mistake in the future 2 pts

d 20 g If 90 g of sodium nitrate NaNO3 is dissolved in 100 g of water at 40 C then the solution is a Unsaturated b Super saturated c Saturated d Cannot be determined from the graph of water at 30 C

Use the following balanced chemical equation to answer the questions below CaBr2 Na2SO4 CaSO4 2NaBr 1 How many moles of sodium bromide can be made from 5 moles of calcium bromide 2 How many grams of calcium sulfate will be made from 2 00 moles of calcium bromide 3 How many grams of calcium bromide will be needed to make 845 grams of calcium sulfate

Predict the products for each of the following D Pd D Lindlar

5 How many moles of water are needed to produce 7 65 moles of hydroge uoride BF3 H2O HF H3BO3

On the phase diagram below region corresponds to the conditions of temperature and pressure under which the solid phase is stable Pressure Select one a D b C c A d E e B A D B Temperature C

9 How many grams in 2 5 moles of potassium hypochlorite

Which of the following pure substances experience London dispersion forces Select one O a none of these O b BH3 O c CH4 O d NH3 Oe all of these

b Consider the RADICAL reaction shown below i Predict the major product and byproduct Then draw the FULL electron pushing mechanism for the reaction including ALL intermediates with lone pairs and formal charges and ALL electron pushing arrows ii Initiation Propagation Br hv A

A compound has a molecular weight of 477 18 g mol and an empirical formula of C10H7O2 What is the molecular formula Select the correct answer below O C30 H2106 O C4H1303 O C14H1203 none of the above

Reaction C3H8 g 502 g 3CO2 g 4H O g If a scientist completely reacts 353 8grams of oxygen gas O with excess propane C3H how many particles in moles of carbon dioxide is likely to form Round any atomic masses on the periodic table to one decimal place

The picture below shows how an object in the sky appears to several hours Early Morning Noon What causes the object to appear to move in this way A the sun revolving B Earth revolving C the sun rotating D Earth rotating To revolve means to move in a path around another object whereas to rotate means to spin Late Afternoon

NH4 2SO4 Ca OH 2 2NH3 CaSO4 2H O For the balanced equation above determine the approximate mass of ammonia NH3 that is created from excess ammonium sulfate and 2 3 mo of calcium hydroxide 0 068 g 39 g 78 g 0 27 g 52 g

the following would increase the par pressure of B at equilibrium A s B g C g AH 0 A adding A B increasing the total volume of the container C increasing the temperature D removing C 54 F Cloudy

6 What is the Percent Composition of all elements in the compound from Question Show your work CH CH OH

6 Write a balanced nuclear equation for the Beta decay of a Nitrogen 16 b Potassium 40 7 Write a balanced nuclear equation for the Alpha decay of a Plutonium 244 b Strontium 90 Man of 25

During its orbit the Earth s minimum distance from the sun is approximately 148 million kilometers Which of the following correctly represents this number in scientific notation O 1 48 x 108 O 1 48 x 104 1 48 x 10 7 O 148 000 000

Give the expression for Keq for the reverse reaction All are gases in a closed container C H6 2Cl C H4Cl 2HCl The concentrations for both Cl and HCI are squared due to their coefficients a H O b OH i C H30 j H S r 0 5000 S 5 5 X 105 x 5 5 x 102 dd 0 7100 C C H6 y 0 7000 ee 1 26 x 10 d C H4Cl k HS 1 52 t 3 5 X 10 Z 1 60 x 105 ff 4 901 f HCl e Cl m HX 0 1 u 8 00 x 105 V 1 75 x 10 aa 1 143 x 105 88 7 93 hh 4 942 g H SO3 h HC H30 p 2 q 3 W 1 11 x 10 bb 0 4900 ii 4 957 CC 1 104 x 105

How many moles and molecules is in 30 g of NaOH hint calculate the MW 1st Show all of your work for full credit 2 pts

The equilibrium constant expression K equals products over reactants depends on the for the reaction Select one a stoichiometry and mechanism b mechanism c presence of a catalyst d stoichiometry e the initial quantities of reactants and products

26 How many moles of oxygen are needed to produce 118g of carbon dioxide combustion of ethane C H6 C2H6 O2 CO H O

Which statement is not correct for Fischer projection OA A chiral carbon is at the intersection of horizontal and vertical lines B Rotation of 180 in plane doesn t change the molecule O C Rotation of 90 is allowed D Both A B Horizontal lines are forward

Enter the symbol for the element being described Enter only the elemental symbol not the name Note If there is more than one possible correct answer full credit will be given for any you choose Element in Period 3 Group 6A

28 If you have 65 g of AuCl3 and 73 g of KOH what is the limiting reactant AuCl3 KOH Au OH 3 KCI

Approximately how many grams of potassium chloride KCI can dissolve in 250 mL of water at 42 C a 100 g b 40 g 38 g 16 g c d

Question 1 What is the total number of moles in 80 grams of C H5CI formula mass of C H5CI 64 5 grams mole Hint use dimensional analysis to solve

For a GAS dissolved in a liquid solution like soda water as the PRESSURE above the liquid increases the solubility of the gas relationship sa

Reaction C3H8 g 5O2 g 3CO2 g 4H O g If a scientist completely reacts 382 1grams of propane C3H8 with excess oxygen gas O what mass of water is likely to form Round any atomic masses on the periodic table to one decimal place

An experiment calls for using 500mL of 4 M hydrochloric acid HCI In the chemical stock room there is only a bottle of 10 M HCI present though How many milliliters of the 10M HCI would the student need to get in order to dilute it down to 4M and have a final volume of 500mL Hint M V M V Show your work 2 points

21 Calculate the volume of 25 g of O that has a pressure of 1 8 atm at 50 C 2 pts

5 Board A cylinder filled with chlorine gas has a radius of 650 cm and a height of 10 m What is the cylinders mass 1 Point O4 138 9 Kg 1 281 7 Kg 128 170 Kg 413 890 Ka

Of the following equilibria only decrease in volume Select one O a N g 3H g 2NH3 g O b 2503 g 25O2 g O2 g O c H g Cl g 2HCl g O d 4Fe s 302 g 2Fe O3 s will sh

35 grams of ethanol is dissolved in 115 grams of water What is the concentration of ethanol in by mass

ystem in a saturated solution of the salt is shown by the following equation ly soluble salt with the general formula AaBb The equilibrium AaBb aA bB Mathematically express the solubility product constant Ksp at equilibrium 16 A 1 L saturated solution of AgCl is evaporated to dryness and the residue is equivalent to 2 68 x 105 mol What is the experimental Kp of the silver sp chloride AgCl s Ag aq Cl aq

Fill in the missing symbol and name the reaction 3 H 1 1 2 3 4 232 U2 Th 92 228 90 144 14 Ce 4Pr Ce 58 59 65 55 Zn 30 40 40 K Ar 18 0 je He

Explain the DEPI NMR data and how it corr to this molecular sturcture 90 45 OH lates