Page 245 - Chemistry eBook

72 Explain, in terms of electronegativity difference, why the bond between hydrogen and
oxygen in a water molecule is more polar than the bond between hydrogen and nitrogen in an ammonia molecule. [1]
Base your answers to questions 74 through 76 on the information below.
73 In the space in your answer booklet, draw a Lewis electron-dot diagram for the reactant containing nitrogen in the equation. [1]
A student prepared two mixtures, each in a labeled beaker. Enough water at 20.°C was used to make 100 milliliters of each mixture.
Sample Regents Questions
Base your answers to questions 74 through 76 on the information below.
used to make 100 milliliters of each mixture.
d
n
of
g
7 g/cm3
ogeneous.” [1]
Information about Two Mixtures at 20.°C
A student prepared two mixtures, each in a labeled beaker. Enough water at 20.°C was
Mixture 1
Mixture 2
Composition NaCl in H2O Fe filings in H2O Information about Two Mixtures at 20.°C
ottom
15.9 = 7.8
74Cl “heter
Student
Composition
Observatio
Student Observations
Other Data
Other Data
assify each mix
s
2
• cMoixloturrles1s liqui
• no visible solid
NaCl in H O
bottom of bea
• colorless liquid
• no visible solid on
• mass of NaCl(
bottom of beaker
dissolved = 2.
• mass of NaCl(s) dissolved = 2.9 g
ture using the term “
74 Classify each mixture using the term “homogeneous” or the term “heterogeneous.” [1]
75 Determine the volume of the Fe filings used to produce mixture 2. [1]
75 Determine the volume of the Fe filings used to produce mixture 2. [1]
76 Describe a procedure to physically remove the water from mixture 1. [1]
ker beaker
76 Describe a procedure to physically remove the water from mixture 1. [1]
June 2011 #75
P.S./Chem.–June ’11
P.S./Chem.–June ’11
2.02 cm3 Explanation:
[12]
Answer
[12]
Table T
Important Formulas and Equations
Density
m d = density d = V m = mass
V = volume
1. We find the mass and density of mixture 2 on the McohlaertCtahlcatuliastipoanrst of the qnuemstbieorno.f moles = given mass
Mass: 15.9 g
Density: 7.87 g/cm3
2.PeNrocwe,ntjuEstrrpolrug in the valu%eserfrroorm= the density table
on Reffy, Table T (p.12) and solve.
Percent Composition % composition by mass = mass of part mass of whole
gram-formula mass
measured value – accepted value
accepted value
× 100 × 100
Answer: 2.02 cm3
M•cixotulorerle2ssliquid
on • black solid on b
Fe filings in H2O
• colorless liquid
• black solid on bottom of
s)beaker • mass of Fe(s) = 9 g • density of Fe(s)
• mass of Fe(s) = 15.9 g
• density of Fe(s) = 7.87 g/cm3
homogeneous” or the term
UNIT 6: MATH IN CHEMISTRY © 244
mass of solute