Chemistry 103 Lecture 20
Dec 19, 2015
Chemistry 103
Lecture 20
Chemical Calculations A mixture of 25.0g of H2 and an excess of N2 react
according to the following equation:
3H2(g) + N2(g) -----> 2NH3(g)
How many liters of NH3 are produced at STP?
Chemical Calculations A mixture of 25.0g of H2 and an excess of N2 react
according to the following equation:
3H2(g) + N2(g) -----> 2NH3(g)
How many liters of NH3 are produced at STP 745mmHg and 23oC?
Outline
I. Solutions - vocabulary - Molarity defined - Solution Stoichiometry
SOLUTIONS - Chapter 12
Matter
Pure Substance Mixture
Element Compound Heterogeneous Homogeneous
Matter
Pure Substance Mixture
Element Compound Heterogeneous Homogeneous
(Solutions)
Mixtures
Homogeneous Mixtures (solutions) The composition is uniform throughout The different parts of the mixture are not visible air, salt water, alloys (i.e. brass, bronze)
Heterogeneous Mixtures The composition of substances is not uniform The composition varies from one part of the mixture to another The different parts of the mixture are visible potting soil, oil and water
Solution vocabulary
Solute - that which is dispersed in a solution (present in lesser amount)
Reacting Component!!!!! Solvent - dispersing agent (present in
greatest amount)
Solutes Spread evenly
throughout the solution.
Are not visible, but can give a color to the solution.
Nature of Solutes in Solutions
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Formation of a Solution
Na+ and Cl- ions• On the surface of a
NaCl crystal are attracted to polar water molecules.
• In solution are hydrated as several H2O molecules surround each.
Copyright © 2008 by Pearson Education, Inc.Publishing as Benjamin Cummings
Solution vocabulary - UnsaturatedUnsaturated solutions Contain less than the
maximum amount of solute.
Can dissolve more solute. Dissolved
solute
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
Solution vocabulary - SaturatedSaturated solutions Contain the
maximum amount of solute that can dissolve.
Have undissolved solute at the bottom of the container.
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
Concentration Terms
Concentration Designates the amount of solute dissolved in a given
quantity of solution
There are many ways of designating concentration. Percent concentration
Percent by mass (m/m) Percent by volume (v/v)
Molarity = M
Molarity
Molarity (M) A Conversion Factor between the amount of solute
and the volume of solution!!!
M = Molarity = moles of solute
L of solution
Making a Solution Steps for making a solution:
1. Weigh out the solute, put it in a volumetric flask.
2. Add some water, mix the solute and the solvent.
3. Add water to the line on the volumetric flask.
Molarity Problems
Calculate the Molarity of 73.0g of HCl in 2.00L of solution.
Calculate the grams of solute needed to prepare 325mL of a 0.100M CaCl2 solution.
Molarity in Chemical Reactions In a chemical reaction, The volume and molarity of a solution are used to determine
the moles of a reactant or product.
M ( mol ) x volume (L) = moles solute L
If molarity, M (mol/L), and moles are given, the volume (L) can be determined.moles x 1 L = volume (L) solution moles
Summary of Chemical Reactions
Copyright © 2008 by Pearson Education, Inc.Publishing as Benjamin Cummings
Using Molarity of ReactantsHow many mL of 3.00 M HCl solution are needed to
completely react with 4.85 g CaCO3?2HCl(aq) + CaCO3(s) CaCl2(aq) + CO2(g) + H2O(l)
Learning Check
How many mL of a 0.150 M Na2S solution are needed to completely react 18.5 mL of 0.225 M NiCl2 solution?
NiCl2(aq) + Na2S(aq) NiS(s) + 2NaCl(aq)
Learning Check
What volume, in liters, of H2 gas measured at STP can be produced from 50.0mL of 6.0M H2SO4 solution and 25.0g of Ni according to the reaction:
Ni(s) + H2SO4(aq) ------> NiSO4(aq) + H2(g)