Lab 8, MOLE RATIOS IN A CHEMICAL REACTION - PowerPoint PPT Presentation

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Lab 8, MOLE RATIOS IN A CHEMICAL REACTION

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Lab 8, MOLE RATIOS IN A CHEMICAL REACTION NaHCO3(S) + HCl(aq) CO2 (g) + H2O(g) + NaCl(S) MATERIALS 150 mL beaker, pipet, small beaker, balance, weighing paper ... – PowerPoint PPT presentation

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Title: Lab 8, MOLE RATIOS IN A CHEMICAL REACTION


1
Lab 8, MOLE RATIOS IN A CHEMICAL REACTION
NaHCO3(S) HCl(aq) ? CO2 (g) H2O(g)
NaCl(S)
  • MATERIALS
  • 150 mL beaker, pipet, small beaker, balance,
    weighing paper, hotplate, sodiumhydrogencarbonate
    (s) and HCl (aq) 3.0 M.
  • SAFETY
  • STUDENTS MUST WEAR GOGGLES, APRONS AND GLOVES
    THROUGHOUT, DO NOT REMOVE UNTILL YOU ARE TOLD TO
    DO SO.
  • PROCEDURE
  • Mass a 150.0 mL beaker, record the mass in your
    lab notebook.
  • Mass 2.00 grams of NaHCO3 in the beaker.
  • Obtain about 30. mL of 3.0 M HCl in a small
    beaker. Keep the beaker in your sink when not in
    use.
  • Obtain a plastic pipet, fill it with HCl
    solution.

2
  • PROCEDURE
  • SLOWLY add the HCl drop wise to the NaHCO3 in
    the beaker and agitate the mixture by swirling.
    The effervescence is the carbon dioxide escaping.
    You should count the drops of HCl added and
    record that data.
  • When all of the solid NaHCO3 has dissolved AND
    the fizzing has stopped, you are finished adding
    acid.
  • After the HCl has been added, place the beaker on
    a hotplate and GENTLY boil off the water.
  • When the salt looks dry, mass the beaker
    containing the salt and record the mass. Place
    the beaker back on the hot plate for 2 min and
    mass a second time. Continue to mass and heat
    until the mass is constant.
  • Subtract the mass of the empty beaker from the
    beaker containing the salt to get the
    EXPERIMENTAL yield of salt.

3
Lab 8, MOLE RATIOS IN A CHEMICAL REACTION
NaHCO3(S) HCl(aq) ? CO2 (g) H2O(g)
NaCl(S)
  • OVERVIEW
  • TO COMPARE TWO DIFFERENT COMPOUNDS YOU MUST
  • IDENTIFY THE KNOWN COMPOUND, THEN CONVERT THE
    KNOWN TO MOLES.
  • RATIO MOLES OF THE KNOWN TO MOLES OF THE
    OBJECTIVE USING THE COEFFICIENTS OF THE BALANCED
    REACTION.
  • CONVERT THE MOLES OF THE OBJECTIVE TO THE UNITS
    REQUIRED.

4
  • RULES TO KNOW
  • DISREGARD SUBSCRIPTS WHEN ASSESSING REACTION
    RATIOS, USE THE COEFFICIENTS.
  • DISCREGRD REACTION COEFFICIENTS WHEN CALCULATING
    MOLAR MASS.
  • GAS VOLUMES CAN BE USED IN RATIOS WITH REACTION
    COEFFICIENTS AT STP.

THE PROCESS STRUCTURE OR SUFFER!
STEP 3 CONVERT OBJECTIVE TO UNITS REQUIRED
MOLES OF OBJECTIVE
STEP ONE CONVERT KNOWN TO MOLES
STEP TWO-MOLE RATIO MOL KNOWN COEF KNOWN MOL
OBJ COEF OBJ
MOLES OF KNOWN
5
  • THE PROCESS STEP ONE ?
  • IDENTIFY THE KNOWN YOU MASSED 2.0 g
  • OF NaHCO3 IN THE LAB, THAT IS YOUR KNOWN,
  • 2) CONVERT THE 2.0 g. OF NaHCO3 TO MOLES.
  • 3) THE EQUATION
    WHICH RELATES MOLE TO GRAMS.

STEP ONE CONVERT KNOWN TO MOLES
MOL MASS G.F.M.
MOL 2.00 g 0.02380 MOL
84.0g/mol
NaHCO3,
The moles you will use in step two.
THE PROCESS STEP TWO ??? ? NaHCO3(S) HCl(aq)
? CO2(aq) H2O(g) NaCl(S) NaHCO3 1
0.02380 mol X 0.02380 mol NaCl(s) NaCl
1 X

STEP TWO-MOLE RATIO MOL KNOWN COEF KNOWN MOL
OBJ COEF OBJ
6
  • THE PROCESS STEP THREE ??
  • IN THIS LAB, YOU MASS YOUR PRODUCT IN
  • GRAMS ON THE ELECTRONIC BALANCE. THEREFORE
  • WE CALCULATE THE THEORETICAL YEILD IN GRAMS,
  • THE REQUIRED UNIT FOR OUR OBJECTIVE NaCl.

STEP 3 CONVERT OBJECTIVE TO UNITS REQUIRED
MOL MASS G.F.M.
0.02380 Mol X g 1.3804 g NaCl
(accepted yield) 58.0
g/Mol
THIS IS THE MASS OF SALT (NaCl) YOU SHOULD HAVE
COLLECTED IN THE LAB, ASSUMMING YOU STARTED WITH
2.0 GRAMS OF NaHCO3. IF YOU USED ANNOTHER MASS OF
THE NaHCO3 TO START WITH, THIS PROCESS WOULD GIVE
A DIFFERENT ACCEPTED VALUE. THE MASS YOU
CALCULATE IS ALSO CALLED THEORETICAL YEILD. WE
WILL ROUND THIS TO 1.38 g (3 SIG FIG) AS THE MASS
IS 3 SIG. FIG.
7
  • THE LAB WRITEUP
  • THE ABSTRACT SHOULD BE A SUMMARY OF ALL THE LAB
    AND ITS RESULTS.
  • LIST ALL OF YOUR DATA THE MASS OF THE EMPTY
    beaker.
  • THE MASS OF THE NaHCO3 YOU MASSED. SHOW THE MASS
    OF WIEGHTING PAPER IF YOU DID NOT TARE THE
    ELECTRONIC BALANCE.
  • SHOW THE MASS OF THE beaker AFTER YOU HAVE HEATED
    TO CONSTANT MASS, SHOW ALL MASSES DURING THE
    HEATING CYCLE.
  • THE FINAL MASS OF THE beaker AND DRY SALT SHOULD
    BE SUBTRACTED FROM THE EMPTY beaker. THIS MASS IS
    YOUR EXPERIMENTAL MASS (YIELD) OF THE OBJECTIVE
    NaCl.
  • DO THE 3 STEP CALCULATION WITH THE MASS OF NaHCO3
    YOU ACUALLY USED IN LAB, EVEN IF IT IS 2.00G, DO
    THE CALCULATION IN YOUR OWN HANDWRITTING WITH
    EXTENSIVE EXPLINATIONS FOR EACH STEP. SHOW MOLAR
    MASS CALCULATION.
  • USE THE FOLLOWING EQUATION TO CALCULATE YOUR
    ERROR.
  • WRITE A CONLUSION BASED ON THE ACCEPTED(CALCULATED
    ) SALT MASS (YEILD) COMPARED TO THE SALT MASS
    (YEILD) YOU ACTUALLY HAD IN THE LAB THAT DAY IN
    REALLITY. DO THE QUESTIONS ON NEXT SLIDE?

ERROR ACCEPTED EXPERIMENTAL X 100
ACCEPTED
EXAMPLE IF YOU COLLECTED 1.20 g OF SALT IN THE
LAB (EXPERIMENTAL). WE CALCULATED THE ACCEPTED
VALUE AS 1.38 g.
ERROR ACCEPTED EXPERIMENTAL X 100
ACCEPTED
ERROR 1.38 1.20 X 100 13.0
1.38
8
  • PLACE THESE QUESTIONS AT THE END OF YOUR LAB
    REPORT, be neat and show all structured work.
  • 1) BASE YOUR ANSWERS FOR QUESTION ONE ON THE
    FOLLOWING REACTION
  • NaHCO3(S) HCl(aq) ? CO2 (aq) H2O(g) NaCl(S)
  • Calculate the moles of NaHCO3 in 8 grams of this
    compound?
  • Can you ratio grams with coefficients?
  • If the 8 grams of NaHCO3 reacts in the above
    reaction, how many moles of salt (NaCl) should be
    produced?
  • If only 6.0 grams of NaCl is collected, what is
    error.
  • How many grams would the NaCl produced (in part
    b) ) weigh in grams?
  • How many moles of H2O would result from the
    reaction of the 8.0 grams of NaHCO3?
  • 2) FOR THE REACTION 3H2 N2 ? 2NH 3, CALCULATE
    THE FOLLOWING
  • a) If 56.0 grams of N2 react, how many moles is
    that?
  • b) If all of the N2 from part a) reacts, how
    many moles of NH3 should be produced.
  • c) What would the NH3 produced in part b) weigh
    in grams.
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