1) When ionic solids dissolve in water, they produce soluble aqueous cations and
ID: 717006 • Letter: 1
Question
1) When ionic solids dissolve in water, they produce soluble aqueous cations and anions. For example, adding MgBr2 solids to water will produce ions according to the dissolution reaction below.
MgBr2(s) Mg2+(aq) + 2 Br(aq)
cation anion
In this lab, you will be observing the color of emission from ions dissolved in solution. Please write the dissolution reaction for each of the ionic solids below. (Use the lowest possible coefficients. Include states-of-matter under the given conditions in your answer.)
(a) LiNO3
(b) SrCl2
(c) Sr(NO3)2
2)The following questions deal with the nature of light and color. (Enter your answers using scientific notation.)
(a) A photon has a wavelength of 500. nanometers (nm). What is the length in meters?
______ m
(b) What is the frequency of this photon?
______ s1
(c) What is the energy of this photon?
______ J
Explanation / Answer
1)
a) LiNO3 --->Li2O+NO2+O2
For balancing;
4LiNO3 --->2Li2O(aq)+4NO2(aq)+O2 (g)
b) SrCl2 -->Sr2+(aq)+Cl-(aq)
c)Sr(NO3)2 --->Sr2+(aq) + 2NO3-(aq)
2)
a)Wave length (p)=500nm=500*10-9 nm=5*10-7m
b)frequency(f)=c/p (here c is velocity of light =3*108)
=(3*108)/(5*10-7) =6*1014Hz
c)energy (E)=hf (hdere h = planck constant =6.62*10-34 j.s)
=6.62*10-34*6*1014 =3.972*10-19 j
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