Calculations
pH
REDOX
Precipitates
Energy
Rates
Balancing
100
What is the mass of 5 moles Ca(NO3)2?
820 g Why?
5 moles x 164 g/mol = 820 g
100
Is H2CO3 a strong acid, strong base, weak acid, weak base, or neutral salt?
weak acid
100
What charge does each oxygen atom become when substances go through combustion?
-2
100
Which cations are always soluble in water?
Alkali Metals
Li, Na, K, Rb, Cs, etc.
Also, NH4+
100
If the surrounding temperature increases, then the reaction is ( endothermic / exothermic ).
exothermic
100
What are 2 things you can do to slow down a reaction?
cool it
dilute it (lower concentration)
100
? H2+1 O2-->2 H2O
What is the coefficient of H2?
2
200
How many moles are 300 Ar atoms?
5 x 10-22 moles Why?
300 atoms / (6 x 1023 atoms/mole) = 5 x 10-22
200
What is the pH of distilled water?
7 Why?
Distilled Water is pure H2O which is neutral.
200
When Ca reacts with oxygen gas, each Ca atom ( gains / loses ) (how many) electrons.
loses 2
200
Is BaSO4 soluble or insoluble in water?
insoluble
200
When 2 solutions are mixed together, the resulting solution feels cold to touch. The reaction between these two solutions is ( endothermic / exothermic ).
endothermic
200
If you dilute a reactant, the reaction will take ( less / more ) time to complete.
more
200
_Al +_NaCl -->_AlCl3 +_Na
Write the balanced chemical equation.
1 Al + 3 NaCl --> 1 AlCl3 + 3 Na
300
4 Al + 3 O2 --> 2 Al2O3
How many moles of O2 gas react with 216 g Al?
6 moles O2 Why?
216 g Al / (27 g/mol) = 8 moles Al
8 moles Al is 2x more than 4
so moles O2 will be 2x more than 3.
300
Write the chemical equation for the dissociation of HCN in water.
HCN + H2O <----> H3O+ + CN-
300
K + NaCl --> KCl + Na
Which element went through reduction?
Na Why?
It's charge decreased from +1 to 0.
300
CaCl2+AgNO3-->Ca(NO3)2+AgCl
What is the precipitate?
AgCl
300
4 Fe + 3 O2 --> 2 Fe2O3 + 822 kJ
Is this reaction endothermic or exothermic?
exothermic
300
What are 3 things that could increase the rate of a reaction.
heat it
increase concentration (add solute, evaporate water)
add catalyst
300
___ CaCl2 + ___ K3PO4 --> ___ KCl + ___ Ca3(PO4)2
What are the coefficients of this chemical equation when it is balanced? Write them in order, separated by commas.
3, 2, 6, 1
400
4 mL of 0.05 M KOH was added to 20 mL of HCl until a color change was seen. What was the initial pH of the original HCl solution?
3
400
Describe the 2 color changes that would occur if you:
(1) Add phenolphthalein to KOH until a color change is seen.
(2) Add HCl to that solution until a color change is seen.
Clear --> Pink
Pink --> Clear
400
4 K + O2 --> 2 K2O
Which element went through reduction?
Oxygen
Why? charge decreased from 0 to -2
400
What is the precipitate when K3PO4 is mixed with MgCl2?
Mg3(PO4)2
400
Is this describing an endothermic or exothermic reaction?
Exothermic Why?
PE of reacting chemicals decreased.
The amount PE decreased is the amount of KE that increased, warming up the surroundings.
400
Use collision theory to explain WHY increasing the concentration of a solution makes the reaction occur faster.
when reacting particles are closer together, they take less time to collide.
400
___ P + ___ O2 --> ___ P2O5
Balance this equation.
4 P + 5 O2 --> 2 P2O5
500
How many grams of NaOH must be added to 5 Liters of water to make its pH 12.
2 g Why?
pH = 12 --> pOH = 2 --> [OH-] = 0.01 M
(M) (L) = moles --> (0.01)(5) = 0.05 moles
0.05 moles x 40 g/mol = 2 g
500
If equal moles of HCl and NiOH were mixed together, the resulting solution would have a pH ? 7.
>, <, or = ?
<
Why? HCl is a strong acid; NiOH is a weak base, the product is a weakly acidic salt, making the pH < 7.
500
K + MgCl2 -->2 KCl + Mg
Write the oxidation half reaction.
Mg+2 + 2e-1 --> Mg
500
What 2 aqueous solutions could be mixed together to form a CaCO3 precipitate?
Ca(NO3)2 or CaCl2
with
X2CO3 if x = Li, Na, K, Rb, Cs, or NH4
500
4 Fe + 3 O2 --> 2 Fe2O3 + 822 kJ
How much heat will be released when 111.7 g of Fe metal reacts with oxygen gas?
411 kJ Why?
111.7 g / (55.85 g/mol) = 2 moles
4 moles Fe release 822 kJ
half that number of moles will release half the kJ
500
Use collision theory to explain WHY increasing the temperature of a solution makes the reaction occur faster.
higher temp = faster motion = less time to collide
also
faster motion = more force during collision = higher % of collisions occur with enough energy to break bonds (KE >or= Activation Energy)
500
C4H10 + O2 --> CO2 + H2O
What is the coefficient of O2 when the equation is balanced?
13 .... Why?
2 C4H10 + 13 O2 --> 8 CO2 + 10 H2O