Term Test 2 (practise 2)

Question 1

which of the following elements can be both a bronsted lowry acid and base?

Answer 1

has an H and a negative sign

Question 2

what is the pH given the molarity of a base?

Answer 2

1. turn the base given into a chemical equation
2. use the given molarity and the stoichiometric coefficients to find of OH
3. use the OH concentration and pOH=-log[OH-] to find the pOH
4. use the formula pH=14-pOH to find the pH

Question 3

what is the strategy to find which of the following salts will give rise to an acidic solution?

Answer 3

pick the base that has H

Question 3

what is the pH given the molarity of a base and the kb value?

Answer 3

1. turn the element given into an equation reacting with water
2. use the concentration given to make an ICE table
3. write the kb expression
4. plug in the ICE table values and the Kb values into te Kb expression and solve for x
5. since the x in the OH concentration, use the pOH=-log[OH-] to find pOH
6. use formal pH=14-pOH to find the pH

Question 4

what is the strategy given the pKA of one acid, find the pKa of a similar-looking element?

Answer 4

1. note if the element you are trying to look for is a weak acid or a strong acid
2. if it is weak the pH should be less than 7 and greater than three
3. if it is strong, the pH should be less than 3
4. chose the answer that corresponds with this notion

Question 5

which of the following changes affects the value of the equilibrium constant?

Answer 5

temperature

Question 6

given an equilibrium reaction and the Kp value what is Kc?

Answer 6

the same as Kp

Question 7

what does it mean if the equilibrium constant K is close to 1?

Answer 7

the reaction depends on the stoichiometric coefficients

Question 8

which of the following cannot be units of the rate constant?

Answer 8

1/(Ms^2) because s^2 represents velocity

Question 9

which statement is true for the rate law rate=k[A]^m[B]^n

Answer 9

the exponent must be determined experimentally

Question 10

given a reaction, two rate constants and two temperatures what is the activation energy? what unit will the answer be?

Answer 10

1.use the formula -Ea=-8.3145(ln(ki/k2)/(1/T2-1/T1) to find the activation energy

2the answer will be in kilojoules

Question 11

an element must be heated in order for its reaction to take place. after the system has reached equilibrium, the temperature is increased by 20 degrees celsius. what happens to the partial pressure of CO2 in the flask

Answer 11

it will increase because the reaction is endothermic

“an element must be heated” is a clue that the reaction in requires heat and is endothermic

temperature increases pressure

Question 12

given three equilibrium reactions and their corresponding rate constants what is the equilibrium constant for the given reaction?

Question 13

what is the base acid ratio necessary to make a buffer solution with a pH of 4.44? the Ka for the acid is given

Answer 13

1. find the pKa using the for pKA=-log(ka)
2. use the Henderson hassle back equation and isolate for the ratio of the base and the acie (base/acid)=10^ph-pKa
3. the answer should be the ratio

Question 14

the reaction of an element with another element is first order in the first element given the rate constant value. what is the order of the reaction in the other element?

Answer 14

look at the stoichiometric coefficient

Question 15

given the mols of a substance and the kp value, find the total pressure.

Answer 15

1. make an equation using the element given
2. make and ICE table
3. write Kp expression
4. use the ICE table, Kp value and Kp expression to find the value of x
5. find the total pressure by plugging in x value into the product side of the ICE table and adding the pressure of the elements together

Question 16

when HCl is titrated with NH3 is the solution at the equivalence point acidic, basic, or neutral? write the relevant reactions and explain why

Answer 16

at the equivalence point, the solution will be acidic because HCl is a strong acid and NH3 is a weak base. Since HCl is a strong acid, it will dissociate almost completely (HCl–> H+ + Cl-). NH3 will only dissociate partially (NH3–> NH4+ + OH-). Since there would be more hydronium ions in the solution compared to hydroxide, the hydronium ions will neutralize (overpower) the hydroxides making the solution acidic

Question 17

is it possible for a weak acid solution to have a lower pH than a strong acid solution?

Answer 17

the weak acid can be in a higher amount than a strong acid in a low amount, thus producing more hydronium ions and being more acidic compared to the strong acid.

Question 18

given the half-life, the reaction if first order the initial pressure of a substance and pressure of another element being the product, how many seconds are required for the pressure of the product to reach its concentration

Answer 18

1. write down what I know
2. make an ICE table, solve for x using the concentration of the product
3. solve for k using the formula k=ln2/t1/2
4. use the first order formula t=ln[Ao]-ln[A]/k to find the value of t