A student measures the mass of a 1.00 g aluminum rod as 0.99 g. The best estimate of the percent error with this measurement is |
You need the percent error formula. (1%) |
The most efficient way to determine whether a reaction is an exothermic chemical reaction is to use what piece of equipment? |
exothermic - heat is released So a thermometer or thermometer probe |
2Al(C2H3O2)3 + 3BaSO4 --> Al2(SO4)3 + 3Ba(C2H3O2)2 |
What are the five types of reactions? Double replacement - always start with two compounds and end with two new compounds |
What is the oxidation number of an oxide ion? |
First what is oxide, second look at your periodic table, third -2. |
What is the molarity of a solution with 0.2 moles of potassium permanganate dissolved in enough water to make a 500.0 mL solution? |
What is the molarity formula? What units do you need to have? (0.4M) |
When 92.0g of ethanol (C2H5OH) are vaporized at its boiling point of 78.3C, it requires 78.6 kJ of energy. What is the approximate molar heat of vaporization of ethanol in kJ/mol? |
The unit gives this away! You need kJ/mol. Take your kJ and divided by the number of moles. Be careful do you have moles?? (39.3 kJ/mol) |
What is the density of an aqueous solution that has a mass of 10.081 g and 12.5 mL? |
What is the density equation? Are your units ok? Did you consider sig figs? (.806 g/mL) |
Which element has 16 neutrons, 15 protons and 15 electrons? |
What subatomic particle tells us what elements this is? protons so this is Phosphorus |
Al + 3AgNO3 --> Al(NO3)3 + 3Ag |
Single - always starts with an element and a compound and ends with a new element and compound |
In the formula for barium chloride, (BaCl2), barium is written first because it is -- |
First - Go to your periodic table and find barium Second - What type of element is it? What is its charge? c. the positive ion |
Which of these laboratory techniques is best to separate a solid from a liquid to recover the liquid? |
a solid from a liquid, noodles from the boiling water filtering |
Which of these is NOT required to ensure that stock solutions are free of contamination? |
You don't want to introduce anything foreign into the stock bottle - So its not necessary to store solutions in brown bottles |
Which of these values is most responsible for changing the boiling and freezing points of a solvent? |
Colligative properties - simple adding a solute changes the properties of the solvent, This is why we add salt to the roads in winter time so the water won't freeze d. number of the solute particles |
What is the name of the compound with the formula NH4NO3? |
This has a lot of elements, this is more than just two elements. Think polyatomic ions. ammonium nitrate |
Calculate the number of moles of Li3PO4 in 2.2L of a 0.60M Li3PO4 solution. What does the capital M mean? |
You have to rearrange the formula to LxM = mol Don't forget sig figs 1.3 mol |
N2 + 3F2 <----> 2NF3 |
Equilibrium = constant, this is the key term only one is constant b. the partial pressure of N2, F2 |
If 89.6 joules of heat are needed to heat 20.0 grams of iron from 30.0C to 40.0C, what is the specific heat of the iron in J/g C? |
The units guide us once again!!! Take the Joules and divide by both grams and change in temperature. .448 J/g C |
Which element will most likely form covalent bonds with fluorine? |
What is covalent? What elements does it include? (only nonmetals) carbon |
The physical process of evaporation involves- |
What is happen in evaporation? A liquid is changing to a gas, the compound is unchanged, so nothing can happen with electrons, that eliminates the first three d. overcoming intermolecular forces |
__C2H4 + __O2 --> ___CO2 + ___H2O |
make both sides have the same number of each type of atom C. 3 |
While English physicist JJ Thomson was carrying out experiments on cathode rays, he was able to determine that the rays consisted of particles he called "corpuscles." These particles were later named - |
This question has a lot of junk!! JJ Thomson = electrons b. electrons |
According to the periodic table of the elements, which elements belong to the same period? |
Same period, periods are the horizontal rows gallium, germanium and arsenic |
How many moles are in 2.04 E24 molecules of H2O? |
Think of your mole map!! Avogadro's number 3.39 mol |
What is the name for the FeCl3 using the IUPAC nomenclature rules? |
What kind of formula is this? The first element is a metal or a nonmetal. Don't forget to assign charges d. iron (III) chloride |
An expandable container of oxygen gas has a volume of 125 mL at a temperature of 25.OC. What volume will the gas occupy at 55.0C? |
We have volumes and temps only!!! Must be a Charles Law. What unit does temperature need to be in? 138mL |
Which of these correctly describes how organic catalysts operate in biological reactions? |
catalyst is the only word you need in this problem catalyst always lowers the activation energy c. |
What volume will 35.9 g of hydrogen gas (H2) occupy at STP? |
STP!!! STP!!!STP!!! 1 mol = 22.4 L, careful do you have moles??? 399 L |
__Ca(NO3)2 + __H3PO4 --> __Ca3(PO4)2 + __HNO3 |
same number of each type of atom on each side of the arrow b. 2 |
Increasing the volume of a sealed container will cause the gas particles within the container to - |
You need relationships to volume, you can relate pressure, temperature or moles. The only answer the mentions one of there is d. Boyles law, volume and pressure are indirectly related |
A substance has a molecular formula of C8H10N4O2. The empirical formula is - |
Reduce, reduce,reduce all by the same number in this case divide by 2. b. C4H5N2O |
Create the formula for diboron trioxide. |
This is an easy one! Prefixes become subscripts B2O3 |
What is the name for the compound AlI3? |
Is the first element a metal or a nonmetal? metal That gets rid of b. Does it have more than one charge? no That gets rids of a and c. Your answer is d. |
2C4H10 + 13O2 --> 8CO2 + 10H2O |
Use your units to guide you! Dimensional analysis b. 24.0 mol |
Using only one trial to collect data in an experiment - |
Accuracy and precision are two terms to associate with lab experiments. Accuracy - are you right or wrong? Precision - how reliable is your data, did you get the same results over multiple trials c. less reliable |
A common product of acid-base neutralization reactions is - |
Key word here is neutral and there is one substance we typically associate with neutral pH - water. b. |
An experiment produced 0.10 g CO2 with a volume of 0.056 L at STP. If the accepted density of CO2 at STP is 1.96 g/L, what is the approximate percent error? |
This is a two step problem. First what is the density from the experimental data and then a percent error problem. d. 8.2% |
If the pH of a solution is 4, what is the pOH? |
Quick and easy formula - pH + pOH = 14 pOH = 10 |
A student hypothesizes that bromine (Br) has different chemical properties from krypton (Kr). The periodic table supports this hypothesis by indicating that — |
The question refers to the periodic table, so you must look at it and compare and contrast Br and Kr. Statement a is false b/c Br is a nonmetal. Statement B is false, Br has a heavier molar mass. Statement C is false, they are in different families, Br is a halogen and Kr is a noble gas. Statement D is correct, b/c they are in different families they also have different numbers of valence e-. |