CHEM 161 Test Answers (LATEST UPDATE) ALL ANSWERS CORRECT

CHEM 161 Test Answers CHEM 161 Lecture 1 Answers What are the SI Base Units? length (meter); Mass (kilogram); time (seconds); temperature (kelvin); amount of a substance (mole); electric current (ampere); luminous intensity (candela) What’s the SI Base Unit for length? meter What’s the SI Base Unit for mass? kilogram (kg) What’s the SI Base Unit for time? second (s) What’s the SI Base Unit for amount? mole (m) What’s the SI Base Unit for temperature? Kelvin What’s the SI Base Unit for current? ampere What’s the SI Base Unit for luminous intensity? candela What is Planck’s constant? 6.626 x 10^-34 Js What are the SI prefixes? What do they mean? Tera (T) = 10^12 Giga (G) = 10^9 Mega (M) = 10^6 Kilo (k) = 10^3 Base Unit = 10^0 = 1 Milli (m) = 10^-3 Micro (u) = 10^-6 Nano (n) = 10^-9 Pico (p) = 10^-12 When are standard prefixes used for? Standard prefixes are used for every three powers of 10 What is centi? 10^-2 c Tera T, 10^12, Trillion Giga G, 10^9, billion Mega M 10^6, million Kilo k, 10^3, thousand Milli m, 10^-3, 0.001 Micro u, 10^-6, 0. Nano n, 10^-9, billionth Pico p, 10^-12, trillionth Convert between Milli and Pico given 0.35 mm. 0.35 mm (1m/10-3 mm) (10^-12 p/1 m) What are all the derived units? Area: m², cm² Volume: m³, cm³ Force: N = Newton = kg(m/s²) = kgms⁻²) Energy: Joule = Nm = kg(m²/sec²) Pressure: P = Pascal = N/m² Density: kg/m³ g/cm³ How do you derive Force? Force: N = Newton = kg(m/s²) = kgms⁻²) How do you derive energy? Joule = Nm = kg(m²/sec²) How do you derive pressure? P = Pascal = N/m² How do you derive density? kg/m³ g/cm³ What is a commonly used measure of volume? liter How are a mL and a cm3 related to each other? they are equal 1000 mL = 1000 cm^3 = 1L What’s the difference between mass and weight? Weight: -equivalent to force (unit is Newtons) -a measure of gravitational attraction Mass: -amount of matter -a measure of a body’s inertia Inertia: resistance to change in motion (acceleration) -popcorn: easy to move back and forth -computer: hard to move back and forth Why do we use significant figures? Experimental measurements have an uncertainty. The uncertainty depends on the measuring instrument used A length is measured as 4.98 cm. Assume the uncertainty is in the last digit (4.98 +- 0.01 cm). How many sig figs? 3 How many sig figs in 0.0498? 3 0.0498 +/- 0.0001 m How many sig figs in 0. km? 3 0. +- 0. km How can we prove that no matter how the measurements are converted, they have the same uncertainty? Divide each of the numbers by their uncertainty. For each, the FRACTION UNCERTAINITY IS THE SAME = 1/500. 4.98/ 0.01 cm 0.0498 / 0.0001 m 30. / 0. km Compare preceding zeroes and trailing zeroes. Which ones count as sig figs? Only trailing zeroes or zeroes between other sig figs count as sig figs What is the uncertainty of 48,000? 48,000 +/ 1000 How do you calculate the max/min of an uncertainty? Using the original numbers, take the last decimal point of each of the numbers. For the min, move the number down 1 and for the max, move the number up 1. The difference between the Max and Min is the uncertainty. How do you use sig figs when multiplying or dividing numbers? Keep the same # of sig figs in your final result that is in the LEAST precise measurement of the calculation How do you use sig figs when adding or subtracting numbers? For adding or subtracting, keep the same number of DECIMAL PLACES in your final answer that is in the least precise measurement of the calculation What are the exceptions to sig fig rules? 1. Exact Definitions (how many inches in a foot) 2. Counts of something (# cards in a deck) 3. Integral numbers that are part of an eq (bh/2) infinite # sfs Convert 25 cm into m 25 cm * 1m/100cm = 0.25 m