Zumdahl chemistry 6th edition solutions

Precise and accurate data: Data can be inaccurate due to a systematic error in the measuring device or with the user. For example, a balance may read all masses as weighing 0. A set of measurements that are imprecise implies that all the numbers are not close to each other. Some say that if the average of imprecise data gives the true value, then the data are accurate; a better description is that the data takers are extremely lucky.

Significant figures are the digits we associate with a number. They contain all of the certain digits and the first uncertain digit the first estimated digit. The result of this is the one-significant-figure answer of 0. From Figure 1. A degree unit on the Fahrenheit scale is not a large as a degree unit on the Celsius or Kelvin scales.

For the TF vs. For the TC vs. Elecrolysis of molten sodium chloride to produce sodium and chlorine gas; the explosive reaction between oxygen and hydrogen to produce water; photosynthesis, which converts H2O and CO2 into C6H12O6 and O2; the combustion of gasoline in our car to produce CO2 and H2O Exercises Significant Figures and Unit Conversions More significant figures should be added if a more precise number is known.

When rounding, the last significant figure stays the same if the number after this significant figure is less than 5 and increases by one if the number is greater than or equal to 5. Volume measurements are estimated to one place past the markings on the glassware.

The first graduated cylinder is labeled to 0. The second cylinder, with 0. The approximate volume in the first graduated cylinder is 2. The total volume would be: 2.

The first graduated cylinder is the least precise volume measurement because the uncertainty of this instrument is in the hundredths place, while the uncertainty of the second graduated cylinder is to the thousandths place. It is always the lease precise measurement that limits the precision of a calculation.

Volumes are always estimated to one position past the marked volume increments. The estimated volume of the first beaker is Yes, all volumes could be identical to each other because the more precise volume readings can be rounded to the other volume readings. But because the volumes are in three different measuring devices, each with its own unique uncertainty, we cannot say with certainty that all three beakers contain the same amount of water.

As is always the case, the least precise measurement determines the precision of a calculation. When the result is rounded to the correct number of significant figures, the last significant figure stays the same if the number after this significant figure is less than 5 and increases by one if the number is greater than or equal to 5. The underline shows the last significant figure in the intermediate answers. We will generally round off at intermediate steps in order to show the correct number of significant figures.

However, you should round off at the end of all the mathematical operations in order to avoid round-off error.

The best way to do calculations is to keep track of the correct number of significant figures during intermediate steps, but round off at the end. For this problem, we underlined the last significant figure in the intermediate steps. The average of several numbers can only be as precise as the least precise number.

Averages can be exceptions to the significant figure rules. Appropriate conversion factors are found in Appendix 6. In general, the number of significant figures we use in the conversion factors will be one more than the number of significant figures from the numbers given in the problem.

This is usually sufficient to avoid round-off error. First, convert 26 miles to yards. So the two are the same. For the gasoline car: Thus Because all numbers when solving the equation are exact numbers, the calculated temperatures are also exact numbers. Therefore, is the unit con- 50o X version between a degree on the X scale to a degree on the Celsius scale. For ethanol: Both have the same mass of 1.

Same; both represent Same; both volumes are 1. The same mass of gas occupies a volume that is over 10, times larger than the liquid sample.

Gases are indeed mostly empty space. A gas has molecules that are very far apart from each other, whereas a solid or liquid has molecules that are very close together. An element has the same type of atom, whereas a compound contains two or more different elements. Picture i represents an element that exists as two atoms bonded together like H2 or O2 or N2. Pictures iii and iv contain representations of elements that exist as individual atoms like Ar, Ne, or He. Picture iv represents a gaseous compound.

Note that pictures ii and iii also contain a gaseous compound, but they also both have a gaseous element present. Picture vi represents a mixture of two gaseous elements.

Picture v represents a solid element. Pictures ii and iii both represent a mixture of a gaseous element and a gaseous compound. Solid: rigid; has a fixed volume and shape; slightly compressible Liquid: definite volume but no specific shape; assumes shape of the container; slightly Compressible Gas: no fixed volume or shape; easily compressible Pure substance: has constant composition; can be composed of either compounds or ele- ments Element: substances that cannot be decomposed into simpler substances by chemical or physical means.

Compound: a substance that can be broken down into simpler substances elements by chemical processes. Homogeneous mixture: a mixture of pure substances that has visibly indistinguishable parts.

Heterogeneous mixture: a mixture of pure substances that has visibly distinguishable parts. Solution: a homogeneous mixture; can be a solid, liquid or gas Chemical change: a given substance becomes a new substance or substances with different properties and different composition.

Physical change: changes the form g, l, or s of a substance but does no change the chemical composition of the substance. Homogeneous: Having visibly indistinguishable parts the same throughout.

Heterogeneous: Having visibly distinguishable parts not uniform throughout. Water H2O is a compound because it is made up of two or more different elements. Table salt is usually a homogeneous mixture composed mostly of sodium chloride NaCl , but will usually contain other substances that help absorb water vapor an anticaking agent.

Initially, a mixture is present. The magnesium and sulfur have only been placed together in the same container at this point, but no reaction has occurred. When heated, a reaction occurs. Assuming the magnesium and sulfur had been measured out in exactly the correct ratio for complete reaction, the remains after heating would be a pure compound composed of magnesium and sulfur.

However, if there were an excess of either magnesium or sulfur, the remains after reaction would be a mixture of the compound produced and the excess reactant. Chalk is a compound because it loses mass when heated and appears to change into another substance with different physical properties the hard chalk turns into a crumbly substance. Because vaporized water is still the same substance as solid water H2O , no chemical reaction has occurred.

Sublimation is a physical change. A physical change is a change in the state of a substance solid, liquid, and gas are the three states of matter ; a physical change does not change the chemical composition of the substance. A chemical change is a change in which a given substance is converted into another substance having a different formula composition. Vaporization refers to a liquid converting to a gas, so this is a physical change. The formula composition of the moth ball does not change.

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