The density of ammonia gas under certain conditions is 0.625 g/L. Calculate its density in g/cm.

A particular flask has a mass of 17.4916 g when empty. When filled with ordinary water at 20.0°C (density = 0.9982 g/mL), the mass of the flask is now 43.9616 g. The density of so-called "heavy water" at 20.0°C is 1.1053 g/mL. What will the mass of the flask be when filled with heavy water at 20.0°C?

1. In the olden days, US minted pennies were pure copper, but copper got so expensive that a pure copper penny was worth more than I cent. Modern pennies are composed of zinc and coated with copper. A student determines the mass of a penny to be 2.482 g. After making several scratches in a penny, the student puts the penny into hydrochloric acid, where the zinc (but not the copper) reacts with hydrochloric acid via a single replacement reaction. The hydrogen is collected at 25°C over water. The collected gas occupies 0.899 L at a total pressure of 791 mm Hg. A. Calculate the moles of hydrogen produced in the reaction. (Hint: Use the Table 1. to determine the vapor pressure of water and assume that all of the zinc in the penny dissolves.) B. Write a balanced chemical reaction for zinc and hydrochloric acid. C. Use stoichiometry to calculate the mass of zinc in the penny. D. Determine the percent zinc (by mass) in the penny.

In the United States, car fuel efficiency is expressed in miles per gallon of gasoline. However, fuel efficiency can also be expressed in kilometers per liter of gasoline. If the fuel efficiency of a car is 11.0 km/L, what is its fuel efficiency in miles per gallon? [1 mile = 1.61 km, 1 gallon = 3.79 L]