Heat Energy Problems
Identify the following as either a chemical change or physical change:
- Burning a log in a fireplace
- Starting a car on fire
- Blending fruit to make a smoothie
- Digesting your lunch
chemical
chemical
physical
chemical
Acetic acid has a Ka of 1.8 x 10-5 while formic acid has a Ka of 3.8 x 10-5. Which acid is a stronger acid?
formic acid
Determine the number of protons, neutrons, and electrons in 58N2+
28 protons, 30 neutrons, 26 electrons
Classify the following reaction:
AgNO3 + NaCl > AgCl + NaNO3
double replacement (metathesis)
What is the Ka expression of the following chemical equation?
H3PO4 (aq) + Ca(OH)2 (aq) → Ca3(PO4)2 (s) + H2O (l)
[H3PO4][Ca(OH)2] = Ka
What are the reactants and products present in a combustion reaction?
Reactants: carbon containing compound and oxygen Products: carbon dioxide and water
** heat energy is both a reactant and product
Calculate the pH of a solution with an [OH-] of 8.2 x 10-6 M
pH = 8.9
Fe2O3
Balance the following chemical equation:
H3PO4 + KOH > K3PO4 + H2O
1 H3PO4 + 3 KOH > 1 K3PO4 + 3 H2O
How many grams of K2CO3 are needed to make a 200 mL solution with a molarity of 2.5M?
70g
How many joules of heat are needed to raise the temperature of 10.0g of aluminum from 22oC to 55oC, if the specific heat of aluminum is 0.90 J/goC
297 J
Calculate the pH of a solution with an [H+] of 1.0 x 10-2
pH = 2
Write the name chemical formula of a compound made between sodium and nitrogen
Na3N, sodium nitride
*** ionic compounds end in the suffix -ide
Which species is oxidized and which is reduced in the following reaction?
2 H2(g) + O2(g) >? 2 H2O(l)
H2 - oxidized
O2 - reduced
At 40oC, the solubility of KBr is 80g per 100g of water. If 75g of KBr is added to 180g of water, is this solution saturated or unsaturated?
unsaturated
A 15.75-g piece of iron absorbs 1086.75 joules of heat energy, and its temperature changes from 25°C to 175°C. Calculate the specific heat capacity of iron.
0.46 J/gCo
Find the [H+] of a solution with a pH of 3.3
5.0 x 10-4
What is the electron geometry and bond angles of SCl2?
tetrahedral, 109.5o
Which species is oxidized and which is reduced in the following reaction?
As2O3 + MnO3 >? H3AsO4 + Mn2+
As2O3 - oxidized
MnO3 - reduced
What is the [H3O+] of a solution if the [OH-] is 4.5 x 10-5? Is this solution acidic or basic?
2.22 x 10-10, basic
To what temperature will a 50.0 g piece of glass raise if it absorbs 5275 joules of heat and its specific heat capacity is 0.50 J/g°C? The initial temperature of the glass is 20.0°C.
Tf = 231oC
Find the [OH-] of a solution with a pH of 10.2
1.58 x 10-4
Which of the following bonds are polar covalent?
P-Cl, Br-Br, I-O, Na-F
P-Cl
I-O
Write a balanced chemical equation for the reaction that occurs between CuCO3(s) and H2SO4(aq)
CuCO3(s) and H2SO4(aq) > CuSO4(aq) + CO2(g) + H2O(l)
Will reactants or products be favored at equilibrium?
HNO3 (aq) + H2O (l) > H3O+ (aq) + NO3_ (aq)
(hint: you will need to look at the acid/base strength chart in your notes)
products will be favored