Exam 1
heat 25.0 g of water from 12.5 °C to 25.7 °C
specific heat is 1cal per gram per Celsius degree
~1380 J, 330. cal
~1380 J, 330. cal
[q=m⋅c⋅ΔT
1. ΔT=25.7−12.5= 13.2°C
2. q= 25.0g ⋅ 1.0cal/g°C ⋅ 13.2°C q=330.0 calories
3. q= 330.0cal ⋅ 4.184J/cal q=1380.72]
Write the name Fe(HCO3)3
Iron (III) hydrogen carbonate
The solubility of KI at 20 degrees is 70 solute/100 g H20. Is 245 grams/ 340 grams water saturated?
Yes
[Solubility in 340 g water= 70×100/340 = 238g KI
Since 245 g KI exceeds the solubility limit of 238 g KI, the solution is saturated, and some KI would remain undissolved]
Determine the pH
[H3O+]=2.0x10-8
acidic or basic?
pH=7.7, basic
Draw the orbital diagram of argon
...
1s:↑↓ 2s:↑↓ 2p:↑↓↑↓↑↓ 3s: ↑↓ 3p: ↑↓ ↑↓ ↑↓
How many unpaired electrons does a copper (Cu) atom have in its ground-state electron configuration?
(Atomic number of copper: 29)
A) 1
B) 2
C) 3
D) 4
E) 0
A) 1
[1s2 2s2 2p6 3s2 3p6 4s1 3d10
Arrange in order of increasing electronegativity
Se, Ca, O
Ca, Se, O
How would the following affect the rate of reaction?
a. adding SO2
b. adding catalyst
c. decreasing O2
2SO2 (g)+ O2(g) > 2SO3 (g)
a.increase
b.increase
c.decrease
What is the pKa given Ka=2.5×10−4?
pKa=3.60
pKa=−log(Ka)
pKa=−log(2.5×10−4)
Strongest intermolecular force KCl
ionic
What is the density (g/mL) of a sample of mineral oil if 250 mL has a mass of 0.23 kg?
.92 g/mL
[Density=Volume/Mass
Density=230g/250mL = 0.92g/mL]
3NO2 + H2O > 2HNO3 + NO
How many grams of NO are produced from 15.8 grams of H2O?
26.3 grams of NO
[1.
2. Moles of H2O=15.8/18.02 ≈0.877mol
3. Mass of NO=0.877×30.01≈26.31g ]
In the combustion of methane:
CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g)
Which reactant has the greatest rate of disappearance?
a. CH4
b. O2
c. CO2
d. H2O
e. CH4 and O2 have the same rate of disappearance.
B. O2
- For every 1 mole of CH4 that reacts, 2 moles of O2 are consumed. This means that O2 is used up at twice the rate of CH4.
Complete and balance the equation for each of the following reactions:
CH4 + 2O2 -->
HCl + Zn (s) -->
a. CH4+2O2 --> CO2+ 2H2O
combustion reaction
b. 2HCl +Zn (s) -->H2 (g) +ZnCl2(aq)
single displacement reaction
Indicate the postive and negative side of the dipole and draw the arrow
P and Br
arrow towards Br
There are two naturally occurring isotopes of boron. The isotope has a mass of 10.01 amu with an abundance of 19.80%, and the isotope has a mass of 11.01 amu with an abundance of 80.20%. Calculate the atomic mass for boron using the weighted average mass method.
10.81 amu
[Atomic Mass=(Mass of Isotope 1×Fractional Abundance 1)+(Mass of Isotope 2×Fractional Abundance 2)
Atomic Mass=(10.01×0.1980)+(11.01×0.8020) =10.812amu ]
Predict angle, shape, geometry of NO2+
angle:180 degrees
shape:linear
geometry:linear
[N=8+8+8=24electrons
A=5+6+6−1=16electrons
S=N−A=24−16=8electrons
L=A−S=16−8=8electrons
Calculate Kc, of .30 M of H2, .17 M I2 and 1.66 M HI
H2 + I2 > 2HI
54
[Kc=[HI]2 / [H2][I2]
Kc=(1.66)2 / (0.30)(0.17)
Kc=2.7556 / 0.051 ≈54.03
Identify the conjugate acid-base pairs in each of the following equations and whether the equilibrium mixture contains mostly products or mostly reactants:
NH3(aq)+HNO3(aq)><NH4+(aq) +NO3-(aq)
HNO3(acid)/NO3- and NH4+/NH3 (base) mixture contains mostly products
[HNO3 is a strong acid, meaning it completely dissociates in aqueous solution. Thus, the equilibrium lies far to the right (products dominate).]
Describe the effect of change on the equilibrium
2CH4O (g) + 3O2 g>< 2CO2 (g) + 4H2O g + 1450 KJ
a. Increasing volume
b.adding CO2
c. removing O2
a. product, more mols of g in products
b. reactants
c. reactants
Identify the larger number
I. 7.2×10^4 and 8.2×10^5
II. 0.00052 and 5.4×10-5
III. 12500 and 3.4×10^4
I. 8.2x10^5
II. .00052
III. 3.4x10^4
2H2O2 > 2H2O + O2
How many moles of H2O2 are needed to produce 3.00 moles H20?
3.00 moles of H2O2
[Moles of H2O2 : Moles of H2O=1:1
Moles of H2O2 = Moles of H2O=3.00]
A sample of Ar gas has a volume of 5.40 L with an unknown pressure. The gas has a volume of 9.73 L when the pressure is 3.62 atm, with no change in temperature and amount of gas. What was the initial pressure, in atmospheres, of the gas?
6.52 atm
[P1V1=P2V2 -> P1=P2V2/V1
P1=3.62atm×9.73L/5.40L = 6.52atm
One of the most acidic lakes in the United States is Little Echo Pond in the Adirondacks in New York. Recently, this lake had a pH of 4.2, well below the recommended pH of 6.5.
What is [H3O+] and [OH-] of Little Echo Pond?
[H3O+]=6.3 x10-5
[OH-]=1.6 x10-10
Work:
[H3O+]=10^−4.2 ≈ 6.31×10−5M
we know [H3O+][OH−]=1.0×10−14 M2
[OH−]=1.0×10−14 / 6.31×10−5 ≈1.59×10−10M
Solution A has a pH of 4.5, and solution B has a pH of 6.7
Which solution is more acidic?
What is the [H3O+] in solution A?
solution A is more acidic
3.2x10-5