(*) At one time, chemists thought that the for mula of a binary compound was the simplest formula possible. For example, the chemical formula of water was thought to be HO and that of ammonia was thought to be NH. Given that 0.832 grams of oxygen combines with 0.104 grams of hydrogen, calculate the atomic mass of oxygen based upon HO as the for mula for water. Similarly, given that 0.403 grams of nitrogen combines with 0.0864 grams of hydrogen, calculate the atomic mass of nitrogen based upon NH as the formula for ammonia.

(*) A 40.0-milligrams sample of the compound $\mathrm{X}_{4} \mathrm{O}_{10}$ contains 22.5 milligrams of oxygen atoms. What is the atomic mass of element X?

In one compound of nitrogen and oxygen, 0.615 grams of nitrogen combines with 0.703 grams of oxygen. In another 1.27 grams of nitrogen combines with 2.90 grams of oxygen. Show how these data illustrate the law of multiple proportions.

(*) A 30.450-milligram sample of a chemical known to contain only carbon, hydrogen, oxygen, and sulfur is put into a combustion analysis apparatus, yielding 54.246 milligrams of carbon dioxide and 22.206 milligrams of water. In another experiment, 23.725 milligrams of the compound is reacted with excess oxygen to produce 10.255 milligrams of sulfur dioxide. What is the empirical formula of the compound?

Write two goals that you think would benefit society, and describe an incentive that will accomplish each goal. Goal: ________ Incentive: _________

Describe the distribution and any interesting patterns you notice in the stem-and-leaf plot. Interpret your findings in terms of the number of medals won in the 2016 Summer Olympics.

Horsepower is a unit of power; one horsepower (1 hp) is equivalent to 745 watts. The world record for climbing a 25-feet rope was set by Garvin Smith in Los Angeles in 1947, when he climbed the 25 feet in 4.7 seconds. Assuming that Mr. Smith has a mass of 65 kg, calculate the average power (in both watts and horsepower) that he generated during his climb.

An isotope of iodine used to treat hyperactive thyroids is iodine-131. It forms the iodide ion $I^{-}$. (a) How many protons are there in a nucleus of I and in a nucleus of $\mathbf{I}^{-}$? (b) How many neutrons are there in a nucleus of I and in a nucleus of $\mathbf{I}^{-}$? (c) How many electrons are there in an iodine atom and in an iodide ion?

Determine each product. a. $25 \times 0.31$ b. $7.05 \times 3.72$

Which pair of elements do you expect to be most similar? Why? a. nitrogen and oxygen, b. titanium and gallium, c. lithium and sodium, d. germanium and arsenic, e. argon and bromine

A satellite will travel indefinitely in a circular orbit around a planet if the normal component of the acceleration of the satellite is equal to $g(R / r)^{2}$, where g is the acceleration of gravity at the surface of the planet, R is the radius of the planet, and r is the distance from the center of the planet to the satellite. Knowing that the diameter of the sun is 1.39 Gm and that the acceleration of gravity at its surface is 274 $m/s^2$, determine the radius of the orbit of the indicated planet around the sun assuming that the orbit is circular.

Determine the absolute value of the number. |-4|

Give the number of (valence) d electrons associated with the central metal ion in each of the following complexes: $\mathrm { Na } \left[ \mathrm { Ag } ( \mathrm { CN } ) _ { 2 } \right]$

A physics student measures the speed of sound in air as $352 \mathrm{m} \cdot \mathrm{s}^{-1}$. A reference source lists the speed as being $344 \mathrm{m} \cdot \mathrm{s}^{-1}$. Calculate the percentage error in the student’s experimental result.