The scatter of data, or deviations about the mean or median, are measures of precision. The smaller the deviation, the more precise the measurements. The Mode The mode of a set of data values is the number in the set that appears most frequently. For exam
MULTIPLE CHOICE
1. Invisible rays, emitted from uranium crystals, that affect a photographic plate were discovered by a. Curie b. Becquerel c. Lawrence d. Einstein 2. Elements that have the same atomic numbers but different atomic masses are called a. ion
Estimating the precision of your results can be done by several different methods. Errors: differences between the true or accepted value and the experimental value. Determinate: errors in method or performance that can be discovered and eliminated Indete
PROBLEMS 1. Nitrogen-13 emits beta radiation and decays to carbon-13 with a half-life of 10 minutes. Assume a starting mass of 2.0 g of nitrogen-13. How many grams of that isotope will remain after four half lives? 2. A patient is administered 20 mg of io
Good way to check work & solve problems quickly 1. Round numbers 2. Round to nearest 0.1 or whole # 3. <5 round down 5 round up Example 1: 4517 4520 or 4500 Example 2: 51 X 69 = ? 51 50 69 70
Be aware of how you are rounding and if it will make answer < o
Two isotopes of the same element will have the same number of a. neutrons and electrons c. neutrons and nucleons b. protons and nucleons d. protons and electrons 2. 3. Which sample contains the same number of atoms as 24 grams of carbon? a. 80. g Ar b. 10
LDS the Sears Way
1. Determine how many e- each atom NEEDS 2. Determine how many e- each atom HAS a.
according to e- configuration/OFD/LDS (1) (2) = Total number of e- shared
3. Subtract: CH4
4. Divide: (3)/2 = # of bonds or pairs of e- Examples:
1. 8 + (
Inquiry Determination Lab Conclusion: Based on experimental results of CO2 production, the amount of H+ present increases the production of CO2 by an overall 106% due to the increase of acidity from the vinegar solutions. The percent by mass of the NaHCO3
The essays require ability to present ideas in a logical order and making use of defined chemical principles to explain observations that are cited in the question. About 40 minutes can be spent on this part, or about 10-15 minutes for each question.
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1. How much energy must be absorbed by 20.0 g of water to increase its temperature from 283.0 C to 303.0 C? 2. When 15.0 g of steam drops in temperature from 275.0 C to 250.0 C, how much heat energy is released? 3. How much energy is required to heat 120.