M1 Active Learning Guide exam 1 PDF

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a complete study guide for exam 1, everything that was studied on lectures...

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Chemistry for Health Sciences – CHE105 Module 1 Active Learning Guide

Key Concepts

What are significant figures and how are they used in calculations?

What is scientific notation?

Answers

Significant figures are all the digits in a measured number including one estimated digit.

In scientific notation, a number is written  as y × 10x.  The term y, called the coefficient, is a number between 1 and 10.  The value x is an exponent, which can be any positive or negative whole number. A conversion factor is a term that converts a quantity in one unit to a quantity in another unit.

How are conversion factors used to convert one unit to another?

A conversion factor is formed by taking an equality, such as 2.20 lb = 1 kg, and writing it as a ratio. We can always write a conversion factor in two different ways.

Density is a physical property that relates the mass of a substance to its volume. Density is the ratio of mass (in grams) to volume (in milliliters or cubic centimeters). Calculate the mass in grams of 15.0 mL of a saline solution that has a density of 1.05 g/mL.

How do you calculate density?

Use density (g/mL) to interconvert the mass and volume of a liquid.

SOLUTION

What are isotopes and how are they related to the atomic weight?

Isotopes are atoms of the same element having a different number of neutrons. Most elements in nature exist as a mixture of isotopes. For example, all atoms of the element chlorine contain 17 protons in the nucleus, but some of these atoms have 18 neutrons in the nucleus and some have 20 neutrons. Thus, chlorine has two isotopes with different mass numbers, 35 and 37. These isotopes are often referred to as chlorine-35 and chlorine-37.

Chemistry for Health Sciences – CHE105 Module 1 Active Learning Guide What three categories is the periodic table divided into?

The elements in the periodic table are divided into three categories— metals, nonmetals, and metalloids.

How are atomic size and ionization energy related to location in the periodic table?

The size of atoms increases down a column of the periodic table, as the valence electrons are farther from the nucleus. The size of atoms decreases across a row of the periodic table as the number of protons in the nucleus increases. An increasing number of protons pulls the electrons closer to the nucleus, so the atom gets smaller.

1 L = 1 000 000 μL 1 mL = 1 cm3 = 1 cc

1. List the rules to determine when a zero is a significant figure. Rule [1] zero counts when: Between two nonzero digits

29.05 g—four significant figures 1.0087 mL—five significant figures

At the end of a number with a decimal point

25.70 cm—four significant figures 3.7500 g—five significant figures 620. lb—three significant figures

Rule [2] A zero does not count as a significant figure when it occurs: At the beginning of a number:

0.0245 mg - 3 sign fig 0.008 mL—one significant figure

At the end of a number that does not have a decimal point: 2.

2,570m – 3 sign fig

List the steps to convert a standard number to scientific notation.

Write each number in scientific notation: (a) 2,500; (b) 0.036. Move the decimal point to give a number between 1 and 10.

a. 1.

b. Move the decimal point three places to the left to give the number 2.5.

1.

Move the decimal point two places to the right to give the number 3.6.

Step [2] Multiply the result by 10x, where x is the number of places the decimal point was moved.  If the decimal point is moved to the left, x is positive.  If the decimal point is moved to the right, x is negative. a. Since the decimal point was moved three places to the left, the exponent is +3, and the coefficient is multiplied by 103. Answer: 2,500 = 2.5 × 103 i. ii.

b. Since the decimal point was moved two places to the right, the exponent is −2, and the coefficient is multiplied by 10−2. Answer: 0.036 = 3.6 × 10−2

Chemistry for Health Sciences – CHE105 Module 1 Active Learning Guide a. b.

If the decimal point is moved to the left, x is +. If the decimal point is moved to the right, x is -.

3. Come up with your own analogy for isotopes. Connect this abstract chemistry concept to an aspect of your everyday life. Isotope, one of two or more species of atoms of a chemical element with the same atomic number and position in the periodic table and nearly identical chemical behaviour but with different atomic masses and physical properties. Every chemical element has one or more isotopes. 4.

List the rules for writing electron configuration orbital diagrams (the version that represents orbitals as lines).

1.

Example: Give the orbital diagram for the electronic configuration of the element sulfur.

2.

Step [1] Use the atomic number to determine the number of electrons.  Sulfur has an atomic number of 16, so 16 electrons must be placed in orbitals.

3.

Step [2] Locate the element in the periodic table and use Figure 2.9 to determine the order of orbital filling.  Read the table in blocks from left-to-right, row-by-row, beginning at the upper left corner and ending with the element in question.  Sulfur is located in the p block, so its 3p orbitals are filled with electrons last. Step [3] Give each orbital two electrons until all electrons are used. In filling orbitals of the same energy, place electrons one at a time in the orbitals until they are half-filled.

1.

 For sulfur, add two electrons to each of the 1s, 2s, three 2p, and 3s orbitals (12 electrons used).  To add the remaining four electrons to the 3p orbitals, give one orbital two electrons and place one unpaired electron in the remaining two orbitals. Answer:

5. Write the electron configuration for Galium two different ways (you have three options to choose from). 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p1 or [Ar] 3d10 4s2 4p1 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p1 or [Ar] 4s2 3d10 4p1...