AP Chem Ch. 3 Review

The weight percent of sodium hydroxide dissolved in water is 50%. What is the mole fraction of sodium hydroxide?

0.311

In 1987 the first substance to act as a superconductor at a temperature above that of liquid nitrogen (77 K) was discovered. The approximate formula of that substance is YBa2Cu3O7. Calculate the percent composition by mass of this material

13.3% Y; 41.2% Ba; 28.6% Cu; 16.9% O

The name for CH3CCl2Ch2Ch3 is

2, 2-dichlorobutane

Potassium-40 is a minor isotope found in naturally occurring potassium. It is radioactive and can be detected on simple-radiation counters. How many protons, neutrons, and electrons does potassium-40 have when it is part of K2SO4

21 neutrons, 19 protons, 18 electrons

Cu(s) + 4HNO3(aq) --> Cu(NO3)2(aq) + 2NO2(g) + 2H2O(l) : Each student in a class placed a 2.00 g sample of a mixture of Cu and Al in a beaker and placed the beaker in a fume hood. The students slowly poured 15.0 mL of 15.8 M HNO3 into their beakers. The reaction between the copper in the mixture and the HNO3 is represented by the equation above. The students observed that a brown gas was released from the beakers and that the solutions turned blue, indicating the formation of Cu+2. The solutions were then diluted with distilled water to known volumes. The students determined that the reaction produced 0.010 mol of Cu(NO3)2. Based on the measurement, what was the percent of Cu by mass in the original 2.00 g sample of the mixture?

32%

Fungal laccase, a blue protein found in wood-rotting fungi, is 0.390% Cu by mass. If a fungal laccase molecule contains 4 copper atoms, what is the molar mass of fungal laccase?

6.52 x 10^4 g

A 23.0 g sample of a compound contains 12.0 g of C, 3.0 g of H, and 8.0 g of O. What is the empirical formula of the compound?

C2H6O

Give the empirical formula for vitamin C (C6H9O6)

C3H4O3

A compound contains only carbon, hydrogen, and oxygen. Combustion of 10.68 mg of the compound yields 16.01 mg CO2 and 4.37 mg H2O. The molar mass of the compound is 176.1 g/mol. What are the empirical and molecular formulas of the compound?

C3H4O3; C6H8O6

Many homes in rural America are heated by propane gas, a compound that contains only carbon and hydrogen. Complete combustion of a sample of propane produced 2.641 g CO2 and 1.442 g H2O as the only products. Find the empirical formula of propane.

C3H8

The compound adrenaline contains 56.79% C, 6.56% H, 28.37% O, and 8.28% N by mass. What is the empirical formula for adrenaline?

C8H11O3N

Give the empirical formula for acetylene, C2H2

CH

Give the empirical formula for benzene, C6H6

CH

Give the empirical formula for acetic acid, HC2H3O2

CH2O

Give the empirical formula for glucose, C6H12O6

CH2O

A compound contains only C, H, and N. Combustion of 35.0 mg of the compound produces 33.5 mg CO2 and 41.1 mg H2O. What is the empirical formula of the compound?

CH6N2

Determine the molecular formula of CoC4O4 when it contains 341.94 g/mol

Co2C8O8

When 1.023 g hydrated CuSO4 is heated until the mass no longer decreases, only 0.654 g of CuSO4 is left. What is the formula of the hydrate?

CuSO4∙5 H2O

A sample of solid labeled as NaCl may be impure. A student analyzes the sample and determines that it contains 75 percent chlorine by mass. Pure NaCl contains 61 percent chlorine by mass. What other sample must be added to the sample of NaCl that adds to the amount of Cl without adding too much overall mass?

LiCl

Determine the molecular formula of NPCl2 when it contains 347.64 g/mol

N3P3Cl6

Give the empirical formula for phosphorus pentoxide, P4O10

P2O5

Determine the molecular formula of SN when it contains 184.32 g/mol

S4N4

Determine the molecular formula of SNH when it contains 188.35 g/mol

S4N4H4

If a pure sample of an oxide of sulfur contains 40. percent sulfur and 60. percent oxygen by mass, then the empirical formula of the oxide is

SO3

One of the most commonly used white pigments in paint is a compound of titanium and oxygen that contains 59.9% Ti by mass. Determine the empirical formula of the compound

TiO2

which of the following is not a base SI unit? meter, gram, mole, second

gram

What is meant by "heating to constant mass" in an experiment designed to analyze the number of moles of water present in a hydrated salt?

heating enough times to remove the water mass and find the mass of the anyhydrous compound so that the mass does not change

We can determine ___ if we know the ___ and ___.

molecular formula, molar mass, empirical formula

How many electrons, neutrons, and protons are in an atom of Cr?

more information is needed to answer this question because Cr has more than one isotope, and the isotope is not specified so we can't find the neutrons