Zinc oxide can be used for treating certain skin conditions. Determine the molar mass of ZnO.

A sample of a hydrocarbon (a compound consisting of only carbon and hydrogen) contains 2.59 1023 atoms of hydrogen and is 17.3% hydrogen by mass. If the molar mass of the hydrocarbon is between 55 and 65 g/mol, what amount (moles) of compound is present, and what is the mass of the sample?

3.46 What mass of ozone (O3) contains 4.5 moles of the substance?

Considering your answer to Exercise 79, which type of formula, empirical or molecular, can be obtained from elemental analysis that gives percent composition?

How many moles of beryllium (Be) are needed to completely react with 10.0 moles of N2 in the synthesis of the compound Be3N2?

The reaction of methane and water is one way to prepare hydrogen for use as a fuel: CH4(g) + H2O(g) CO(g) + 3 H2(g) If you begin with 995 g of CH4 and 2510 g of water, (a) Which reactant is the limiting reactant? (b) What is the maximum mass of H2 that can be prepared? (c) What mass of the excess reactant remains when the reaction is completed?

DDT (molar mass = 354.49 g/mol) was a widely used insecticide that was banned from use in the United States in 1973. This ban was brought about due to the persistence of DDT in many different ecosystems, leading to high accumulations of the substance in many birds of prey. The insecticide was shown to cause a thinning of egg shells, pushing many birds toward extinction. If a 20-L drum of DDT was spilled into a pond, resulting in a DDT concentration of 8.75 105 M, how long would it take for the levels of DDT to reach a concentration of 1.41 107 M (a level that is generally assumed safe in mammals)? Assume the decomposition of DDT is a first-order process with a half-life of 56.0 days.

Phenol is a compound of carbon, hydrogen, and oxygen used commonly as a disinfectant. Combustion of a 175-mg sample of phenol yielded 491 mg CO2 and 100. mg H2O. Calculate the empirical formula of phenol. Identify what other information is needed to determine whether the empirical formula is the actual molecular formula.

Nitric acid is produced commercially by the Ostwald process, represented by the following equations: 4NH3(g)+5O24NO(g)+6H2O(g)2NO(g)+O2(g)2NO2(g)3NO2(g)+H2O(l)2HNO3(aq)+NO(g) What mass of NH3 must be used to produce 1.0 106 kg HNO3 by the Ostwald process? Assume 100% yield in each reaction, and assume that the NO produced in the third step is not recycled.

Consider the chemical reaction 2 S + 3 O2 → 2 SO3. If the reaction is run by adding S indefinitely to a fixed amount of O2, which of these graphs best represents the formation of SO3? Explain your choice.