chem 12

Created by brambola 

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# of molecules

this quantity can always be used in the same way as moles when interpreting balanced chemical equations

volume

this is conserved only in reactions where the temp. is constant and the # of moles of gaseous reactants is the same as that of gaseous products

mass

this is conserved in every ordinary chemical reaction

limiting reagent

the reactant that determines the amount of product that can be formed in a reaction

theoretical yield

the max amount of product that could be formed from given amounts of reactants

excess reagent

the reactant that is not completely used up in a reaction

actual yield

the amount of product formed when a reaction is carried out in the lab

percent yield

the ratio of the actual yield to the theoretical yield

stoichiometry

the calculation of quantities in chemical reactions is called

If 1 egg and 1/3 cup of oil are needed for each bag of brownie mix, how many bags of brownie mix do you need if you want to use up all 3 eggs and 1 cup of oil?

3 bags

What is conserved in the reaction shown below? H2(g) + Cl2 (g) --> 2HCl(g)

mass, moles, molecules, and volume..

What is conserved in the reaction shown below?N2(g)+3F2(g)__2NF3(g)

Mass and atoms only.

In every chemical reaction,____.conserved

mass and atoms are conserved

In a chemical reaction, the mass of the products is?

is equal to the mass of the reactants

In any chemical reaction, the quantities that are preserved are___?

mass and number of atoms or (always equal?)

the first step in most stoichiometry problems is to

convert given quantities to mole

In the reaction 2CO(g)+O2(g)-->2CO2(g) what is the raito of the moles of oxygen used to moles of CO2 produced?

1:2

Which of the following is true about the total number of reactants and the total number of products?
C2H12(l) + 8O2 = 5Co2(g) + 6H2O(g)

9 moles of reactants chemically change into 11 moles of products

Which of the following is an INCORRECT interpretation of the balanced equation
shown below? 2S(s) + 3O2(g) --->2SO3(g)

. 2 g S + 3 g O2--> 2 g SO3

. Calculate the number of moles of Al 2O3 that are produced when 0.60 mol of Fe is
produced in the following reaction. 2Al(s) + 3FeO(s) --> 3Fe(s) + Al2O3(s)

0.20 mol

How many moles of aluminum are needed to react completely with 1.2 mol of FeO? 2Al(s) + 3FeO(s) --> 3Fe(s) + Al2O3(s)

0.8 mol

How many moles of glucose, C6H12O6, can be "burned" biologically when 10.0 mol of oxygen is available? C6H12O6 (s) + 6O2 (g) --> 6CO2 (g) + 6H2O(l)

1.67 mole of glucose

Hydrogen gas can be produced by reacting aluminum with sulfuric acid. How many
moles of sulfuric acid are needed to completely react with 15.0 mol of aluminum? 2Al(s) + 3H2SO4 (aq) --> Al2 (SO4 )3 (aq) + 3H2(g)

. 22.5 mol

When iron rusts in air, iron(III) oxide is produced. How many moles of oxygen react with 2.4 mol of iron in the rusting reaction? 4Fe(s) + 3O2(g) --> 2Fe2O3(s)

1.8 mol

At STP, how many liters of oxygen are required to react completely with 3.6 liters of hydrogen to form water? 2H(2) (g) + O(2) (g) -->> 2H(2)O(g)

1.8 Liters

The equation below shows the decomposition of lead nitrate. How many grams of oxygen are produced when 11.5 g NO2 is formed? 2Pb(NO3) 2(s) --> 2PbO(s) + 4NO2 (g) + O2(g

. 2. g

Which type of stoichiometric calculation does not require the use of the molar mass?

volume-volume problems

Iron(III) oxide is formed when iron combines with oxygen in the air. How many grams of Fe2O3 are formed when 16.7 g of Fe reacts completely with oxygen? 4Fe(s) + 3O2(g) --> 2Fe2O3(s)

23.95g

When glucose is consumed, it reacts with oxygen in the body to produce carbon dioxide, water, and energy. How many grams of carbon dioxide would be produced if 45 g of C6H12O6 completely reacted
with oxygen?

. 66 g

Aluminum reacts with sulfuric acid to produce aluminum sulfate and hydrogen gas. How many grams of aluminum sulfate would be formed if 250 g H2SO4 completely reacted with aluminum?
2AL(s) + 3H2SO4 (aq) --> Al2 (SO4)3 (aq) + 3H2 (g)

290 g

Mercury can be obtained by reacting mercury(II) sulfide with calcium oxide. How many grams of calcium oxide are needed to produce 36.0 g of Hg?
4HgS(s) + 4CaO(s) -->4Hg(l) + 3CaS(s) + CaSO4

10.1 g

How many moles of H3PO are produced when 71g P4O10 reacts completely to form H3PO4?

1 mol

How many grams of H3PO4 are produced when 10.0 moles of water react with an excess of P4O10 ? P4O10 (s) + 6H2O(l) --> 4H3PO4 (aq)

653 g

How many liters of hydrogen gas are needed to react with CS2 to produce 2.50 L of CH4 at STP?
4H2(g)+CS2(l) = CH4(g) +2H2S(g)

10.0 L

Which conversion factor do you use first to calculate the number of grams of CO2 produced by the reaction of 50.6 g of CH4 with O2 ? The equation for the complete combustion of methane is: CH4 (g) + 2O2 (g) --> CO2 (g) + 2H2O(l)

1 mol CH4/16.0 g CH4

Which of the following statements is true about the following reaction? 3NaHCO3(aq) + C6H8O7(aq) --> 3CO2(g) + 3H2O(s) +Na3C6H5O7(aq)

1 mole of water is produced for every mole of carbon dioxide produced

How many liters of NH3 are needed to react completely with 30.0 L of NO (at STP)? 4HN3(g) + 6NO(g) ----> 5H2(g) +6H2O(g)

20.0 L

When 0.1 mol of calcium reacts with 880 g of water, 2.24 L of hydrogen gas form (at STP). How would the amount of hydrogen produced change if the volume of water was decreased to 440 mL (440 g)?

The volume of hydrogen produced would be the same.

Glucose, C6H12O6, is a good source of food energy. When it reacts with oxygen, carbon dioxide and water are formed.How many liters of CO2 are produced when 126 grams of glucose completely react with oxygen? C6H12O6 (s) + 6 O2 --> 6 CO2 (g) + 6 H2O (l)

180g produces 6 mole CO2 126g=4.2moles CO2 =184.8g CO2(ml/.00198g)=93333.3ml(1Lt/1000ml)=93... of CO2
(.00198g/ml)=density CO2

Calcium oxide, or lime, is produced by the thermal decomposition of limestone in the reaction CaCO3 (s) --> CaO(s) + CO2(g). What mass of lime can be produced from 1.5 x 10^3 kg of limestone?

8.4 x10^2 kg

When two substances react to form products, the reactant used up is called what?

limiting reactant

Which of the following is NOT true about limiting and excess reagents?

The reactant that has the smallest given mass is the limiting reagent.

How many grams of chromium are needed to react with an excess of CuSO4 to produce 27.0g Cu?
2Cr(s) + 3CuSO4(aq)---->Cr2(SO4)3(aq) + 3Cu(s)

14.7 grams

. How many grams of beryllium are needed to produce 36.0 g of hydrogen? (Assume an
excess of water.) Be(s) + 2H2O(l) --> Be(OH)2 (aq) + H2(g)

162 g

How many liters of NH3, at STP, will react with 5.3g of 02 to form NO2 and water.?

2.12 liters of NH3

How many liters of chlorine gas can be produced when 0.98 L of HCl react with
excess O2 at STP? 4HCl(g) + O2(g) -- >2Cl2 (g) + 2H2O(g)

0.49 L

Identify the limiting reagent and the volume of CO2 formed when 11L Cs2 reacts with 18L O2 to produce CO2 gas and SO2 gas at STP .CS2 (g) + 3O2(g)---->CO2(g) +2SO2(g)

O2

What is the maximum number of grams of PH3 that can be formed when 6.2 g of
phosphorus reacts with 4.0 g of hydrogen to form PH3 ? P4 (g) + 6H2(g) --> 4PH3 (g)

6.8 g

Methane and hydrogen sulfide form when hydrogen reacts with carbon disulfide identify the excess reagent and calculate how much remains after 36 l of h2 reacts with 12 l of cs2 4 h2 g cs2 g ch4 g 2 h2s g

48.03H2

Metallic copper is formed when aluminum reacts with copper(II) sulfate. How many grams of metallic copper can be obtained when 54.0 g of Al react with 319 g of CuSO4 ? Al + 3CuSO4--> Al2 (SO4 )3+ 3Cu

127 g

Which statement is true if 12 mol CO and 12 mol Fe2O3 are allowed to react? 3CO (g) + Fe2O3 (s) ---> 2Fe (s) + 3CO2(g)

limiting reagent: CO and 8.0 mol Fe will be formed.

Which of the following would be the limiting reagent in the reaction shown below? 2H2(g) + O2(g) --> 2H2O(g)

50 molecules of H2

When an equation is used to calculate the amount of product that will form during a reaction then the value obtained is called the what?

theoretical yield

Which of the following is NOT true about "yield"?

The actual yield may be different from the theoretical yield because reactions do not always go to completion.

Which of the following is NOT a reason why actual yield is less than theoretical yield?

conservation of mass

Lead nitrate can be decomposed by heating. What is the percent yield of the decomposition reaction if 9.9 g Pb(NO3 )2 are heated to give 5.5 g of PbO?
2Pb(NO3 )2(s) -->2PbO(s) + 4NO2(g) + O2 (g)

82%

Hydrogen gas is produced when zinc reacts with hydrochloric acid. If the actual yield of this reaction is 85%? how many grams of zinc are needed to produce 112 l of H2 at STP?

380

In a particular reaction between copper metal and silver nitrate, 12.7 g Cu produced 38.1 g Ag. What is the percent yield of silver in this reaction?
Cu + 2AgNO3--> Cu(NO3) 2 + 2Ag

88.2%

mole ratio

a conversion factor derived from the coeff of a balanced chem equatn interprted in terms of moles

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