C.W. BAKER HIGH SCHOOL

CORE III REVIEW QUESTIONS

  STOICHIOMETRY/MOLES

 

Click here for the answers to the following questions

 

Understanding chemical formulas and equations

 

1.     How many H atoms are present in the following formula -  (NH4)3PO4

 

2.     Explain the difference between  2 H  and H2.

 

3.     Draw a diagram showing the atoms to represent the chemical change which takes place in the following reaction:

2 C  +    O2     ------>  2  CO

 

 

4.     An ethene molecule is made up of two carbon atoms held together by a double bond (an alkene) and four hydrogen atoms.  Show the following formulas for ethene.

a)  molecular -

 

b) empirical -

 

c) structural -

 

 

5.     Write the correct formulas for the following compounds:

 

a) Barium chloride

 

b) Aluminum hydroxide

 

c) sodium sulfate

 

d) nitrogen gas

 

e) dinitrogen monoxide

 

f)  carbon tetrachloride

 

g) iron (II) oxide

 

h) iron (III) oxide

 

6.      What do the Roman numerals stand for in the 5-g and 5-h?

 

7.      What general rule should you apply in writing the formulas for compounds?

 

Balance the following equations by adjusting the coefficients (and identify the reaction type):

 

8.     Na        +     CuCl2      ----->      NaCl     +     Cu     (_________________________)

 

9.     Mg      +    O2    ------>   MgO     (_________________________)

 

10.  H2CO3   ----->     H2O    +     CO2     (_________________________)

 

11. C3H8   +    O2   ------>     CO2     +    H2O (_________________________)

 

Molar Mass Problems

 

12.   What is the mass of one mole of Na?

 

13.   What is the mass of 5 moles of sulfur?

 

14.   What is the mass of 1.5 moles of nitrogen gas?

 

15.  What is the molar mass of carbon dioxide?

 

16.  How many moles of water are in a beaker that contains 120 grams of water?

 

Percent Composition problems

 

17. Given that the formula of sodium nitrate is NaNO3, what is the percentage of nitrogen in the compound?

 

 

 

18. A sample of a compound is found to contain 36 grams of carbon and 6 grams of hydrogen.  What is the % of carbon in the compound?  What is the % of hydrogen in the compound?

 

19.  A hydrated compound is found to have the formula of CuSO4.5H2O.  What is the percent water in the hydrate?

 

 

Determining Molecular Formula from Empirical Formulas and Molecular Mass.

 

20. Hydrogen peroxide has a molecular formula of H2O2, what is its empirical formula?

 

21. A compound is found to have an empirical formula of CH and a molecular mass of 78 grams.  What is the molecular formula of the compound?

 

Stoichiometry (Mole Ratios) - Base your answers on the following equation.

 

H2SO4   +   2 NaOH   ----->    Na2SO4   +  2 H-0H

 

22. How many moles of sulfuric acid would be required to produce 5 moles of water?

 

23. How many moles of sodium hydroxide would be required to react with 15 moles of sulfuric acid?

24.  How many moles of water would be produced if .75 moles of sodium hydroxide was used up?

 

Titration Problems

Base your answers to the following questions on this balanced equation:

 

NaOH    +  HCl   ----->    NaCl   + H-OH

 

25. What formula can be used to do the calculations required in a titration problem?

 

 

 

26. 15 ml of .5 Molar sodium hydroxide solution is titrated with .25 Molar hydrochloric acid.  How many ml of acid will be required to neutralize the base?

 

 

 

 

27.  35 ml of .2 Molar acid is used to titrate a 20 ml sample of sodium hydroxide.  What is the molarity of the sodium hydroxide?