Chemistry Final Exam old test questions

About how many moles is 1.2 x 10^18 atoms of tin?

2 x 10^-6 moles

What are the missing coefficients for the equation below? Cr(s) + Fe(NO3)2 (aq) --> Fe(s) + Cr(NO3)3 (aq)

2, 3, 3, 2

When potassium hydroxide and barium chloride react, potassium chloride and barium hydroxide are formed. The balanced equation for this reaction is _____.

2KOH + BaCl2 --> 2KCl + Ba(OH)2

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

0.20 mol

In the following equation, what are the products? What are the reactants? Is the equation balanced? If not, balance it. K2 SO4 (aq) + Ba(NO3)2 (aq) --> BaSO4 (s) + KNO3 (aq)

1. Products= BaSO4 (s) + KNO3 (aq) 2. Reactants= K2 SO4 (aq) + Ba(NO3)2 (aq) 3. Balanced= 1, 1, 1, 2

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

What are the coefficients that will balance the skeleton below? Al Cl3 + NaOH --> Al(OH)3 + NaCl

1, 3, 1, 3

What are the coefficients that will balance the skeleton equation below? N2 + H2 --> NH3

1, 3, 2

How do we use the coefficients in a balanced chemical reaction? List and describe at least 2 different reasons we need to have the right coefficients in place.

1. For the mole to mole ratio, you need to know the coefficients to compare the conversion. The coefficients must be plugged into the equation to complete the problem. 2. You must also have the correct coefficients to show that the reaction maintains the same mass throughout, Balancing the equation properly with coefficients proves the law of conservation of mass to be true.

What is the number of moles in 432 g Ba(NO3)2?

1.65 mol

What is the volume, in liters, of 0.500 mol of C3H8 gas at STP?

11.2 L

Metallic copper is formed when aluminum reacts with copper (II) sulfate. How many gra,s of metallic copper can be obtained when 45.0 g of Al react with 391 g of CuSO4? Al + 3CuSO4 --> Al2(SO4)3 + 3Cu

156 g

What is the mass of oxygen in 250 g of sulfuric acid, H2SO4?

160 g

When the following equation is balanced, the coefficient of sulfur dioxide is ____. PbS (s) + O2 (g) --> PbO (s) + SO2 (g)

2

When the following equation is balanced, what is the coefficient for HCl? Mg(s) + HCl (aq) --> MgCl2 (aq) + H2 (g)

2

What is the percent composition of chromium in BaCrO4?

20.5%

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)

23.9 g

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

27.9 g

What is the percent composition of a compound containing sulfur and chlorine if 35 grams of the compound contains 10 grams of chlorine?

28.6% Cl, 71.4% S

In the reaction 2CO (g) + O2 (g) --> 2CO2 (g), what is the ratio of *moles of CO* used to *moles of O2* used?

2:1

Write the following as a chemical equation: solid aluminum and solid iodine react to produce solid aluminum iodide

2Al (s) + I2 (s) --> 2Al I 3 (s)

Rewrite the following word equation as a balanced chemical equation. What is the coefficient and symbol for flourine? nitrogen triflouride --> nitrogen + flourine

3F2

Balance the following chemical equation. What is the coefficient for H2O? C3 H8 + O2 --> CO2 + H2O

4

How many atoms are in 0.075 mol of titanium?

4.5 x 10^22

How many oxygen atoms are contained in 2.74 g of Al2(SO4)3?

5.79 x 10^22

What is the mass in grams of 5.90 mol C8H18?

673 g

What is the molar mass of (NH4)2CO3?

96 g

Gaseous propylene, C3H6, burns in the air (which means you should add oxygen). A. Write the balanced equation B. How many grams of CO2 can form when a mixture of 6.91 g of C3H6 and 15.2 g O2 is ignited, assuming only the reaction above occurs? Label the limiting reagent C. Using the information in pat b, if 11.37 g of CO2 is formed in lab, what is the percent yield? D. How much of the excess reactant remains, in grams?

A. 2C3H6 (g) + 9O2 --> 6CO2 (g) + 6H2O (l) B. limiting reactant= O2, 13.9 g CO2 C. 122% D. 0.3 g C3H6

Which equation represents the compound formed from these two ions: silver and hydroxide?

AgOH

In order for the reaction 2Al + 6HCl --> 2Al Cl3 + 3H2 to occur, which of the following must be true?

Al must be above H on the activity series

A compound contains 40.0% C, 6.71% H, and 53.29% O by mass. The molecular weight of the compound is 60.05 amu. The molecular formula of this compound is ____.

C2H4O2

An organic acid consists of 64.3% carbon, 7.2% hydrogen, and 28.5% oxygen. What is the empirical formula of this compound?

C3H4O

Which of the following is an empirical formula?

C3H8O

Complete this energy equation. ____ + 6O2 --> 6CO2 + 6H2O + Energy

C6 H12 O6

Table salt contains the elements sodium and chlorine. Identify the chemical formula of this compound.

NaCl

NaHCO3 (s) + HCl (aq) --> NaCl (aq) + H2O(l) + Co2 (g) What are the reactants of this equation?

NaHCO3, HCl

Write the following as a chemical equation: aqueous sodium hydroxide and aqueous hydrochloric acid react to produce liquid water and aqueous sodium chloride

NaOH (aq) + HCl (aq) --> H20 (l) + NaCl (aq)

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

O2; 6.0 L CO2

If a combustion reaction takes place between rubidium and bromine, the chemical formula for the product is:

RbBr

Write the following equation in words: Li (s) + H2O (l) --> LiOH (aq) + H2 (g)

Solid Lithium and liquid water react to produce aqueous Lithium Hydroxide and gaseous hydrogen

How do I know, if the problem doesn't specifically say, that I need to find the limiting reagent in a problem?

There will be two givens

Assuming no errors were made in measuring the yield, can the percent yield of a chemical reaction be greater than 100%? Explain.

Yes, in the case that other variables were in the reaction. Like in the magnesium lab, magnesium reacted with oxygen, but nitrogen is also in the air, pushing the percent yield over 100%.

Balance the following equations: a. __NaCl + __BeF2 --> __NaF + __BeCl2 b. __FeCl3 + __Be3(PO4)2 --> __BeCl2 + __FePO4 c. __AgNO3 + __LiOH --> __AgOH + __LiNO3 d. __CH4 + __O2 --> __CO2 + __H2O e. __Mg + __Mn2O3 --> __MgO + __Mn

a. 2, 1, 2, 1 b. 2, 1, 3, 2 c. balanced d. 1, 2, 1, 2 e. 3, 1, 3, 2

True or False: Can these single replacement reactions occur? a. Zn (s) + CuCl2 (aq) --> Cu (s) + ZnCl2 (aq) b. Cu (s) + AgNO3 (aq) --> Ag (s) + Cu(NO3)2 (aq) c. 2Al (s) + Fe2 O3 (S) --> 2Fe (s) + Al2O3 (s) d. 3Fe(s) + Al2 O3 (s) --> 2Al (s) + 3Fe) (s)

a. true b. true c. true d. false

The atomic masses of any two elements contain the same number of ____.

atoms

The first step in most stoichiometry problems is to ___ __.

balance the equation

The reaction 2Fe + 3Cl2 --> 2FeCl3 is an example of which type of reaction?

combination reaction

The equation 2C 3H7 OH + 9O2 --> 6CO2 + 8H2O is an example of which type of reaction?

combustion reaction

The equation H3 PO4, + 3K OH --> K3 PO3 + 3H2O is an example of which type of reaction?

double-replacement reaction

The lowest whole-number ratio of the elements in a compound is called the ____.

empirical formula

The volume of one mole of a substance is 22.4 L at STP for all ____.

gases

In a chemical reaction, the mass of the products ____.

is equal to the mass of the reactants

The mass of a mole of NaCl is the:

molar mass

Avogrado's number of representative particles is equal to one _____.

mole

A catalyst is:

not used up in a reaction

Give the number of protons, neutrons, and electrons for the potassium ion. 40K+1

p= 19 N= 21 E= 18

A net ionic equation:

shows only those particles involved in the reaction.

The equation Mg (s) + 2HCl (aq) --> MgCl2 (aq) + H2 (g) is an example of which type of reaction?

single-replacement reaction

Chemical equations must be balanced to satisfy:

the law of conservation of mass

Which of the following is equal to Avogrado's number?

the number of molecules of nitrogen in 1 mol N2

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

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