Smallest set is obtained if greatest common factor is 1

Slides:

Advertisements

Similar presentations

QUESTION: A 25.0 gram sample of a compound is found to be 24% chlorine by mass. What is the percentage of chlorine in a 50.0 g sample of the compound?

Advertisements

A mole of atoms contains exactly 6.02x1023 atoms.

Mass of proton : x kg, or u QUESTION: Which of the following has the largest total mass? A. 2 protons + 4 electrons B. 2 neutrons.

QUESTION: Which of the following elements is a transition metal? A. silicon, B. lead, C. sodium, D. chromium SCRIPT: Which of the following elements.

How to tell from the name if a compound is ionic:

SO3: one Sulfur atom: 16 protons

Which of these is the formula of a reactant in this reaction?

Consider the combustion of propane: C3H8 + O2  CO2 + H2O (unbalanced)

Let’s examine the figure to see what molecules are being represented.

What is the molar mass of Ca(NO3)2?

Individual count  / Avogadro’s number  Mole count n = N / NA

Here’s a general strategy for determining empirical formulas.

QUESTION: Consider the following partially-drawn structure of 2-butene (C4H8) where only the C atoms are shown: C-C=C-C When this structure is completed.

PCl5 is a binary, molecular compound. Binary: two elements (P and Cl)

QUESTION: Which of the following is a metalloid? A. Potassium, B. Silicon, C. Iron, D. Helium SCRIPT: Which of the following is a metalloid? A.

In nature, substances are typically mixed.

Mass of proton or neutron: 1.0 u Mass of electron: u

What is the molar mass of NH3?

Trends in atomic size: opposite of trend in ionization energy

CLICK Here are some possible molecular formulas When x=1, we have NO2.

AuCN B. Au(CN)2 C. Au(CN)3 D. Au(CN)4

QUESTION: Which of the following elements is the best electrical conductor? A. carbon, B. germanium, C. manganese, D. iodine SCRIPT: A. carbon,

Ions are formed by loss or gain of electrons.

Ammonium sulfide is an ionic compound. Cation is ammonium ion. NH4+

A. 0.8 g/mL, B g/mL, C g/mL, D. 1.3 g/mL

One Ca2+ ion: +2 One CO32- ion: -2

There are 3 orbitals in a p subshell (ml = -1, 0, or +1).

Ions are formed by loss or gain of electrons.

QUESTION: How many atoms in the acetic acid molecule (CH3COOH) are capable of hydrogen bonding interaction with water molecules? A. 1, B. 2, C. 3, D.

Lower n+l  filled first If same n+l  lower n filled first

The molecule shown in the figure has two blue spheres.

Here’s a general strategy for determining empirical formulas.

Strategy for determining excess:

Mathematically, this implies that the ratio of the amount of element

How many neutrons does an O-18 atom have? A. 8, B. 10, C. 16, D. 18

One Na+ ion: +1 One CO32- ion: -2

QUESTION: How should the result of the following calculation be reported, assuming that 1.8 and 32 are exact numbers? 32 + (1.8)(2.37) A. 36,

Cobalt(II) chloride is an ionic compound. Therefore:

What is the Kelvin temperature equivalent to 50.00oF?

HIGHLIGHT carbon in legend

QUESTION: Assume circles and squares in the figures below represent atoms. According Dalton’s atomic theory, which of the figures below best represents.

The oxygen-to-carbon ratio in that sample is x over 36.0 HIGHLIGHT

What is the Kelvin temperature equivalent to 25.00oC?

Uncertainty is at least +1/10 of smallest interval.

The simplest collection of ions with a total charge of zero would be….

Each calcium ion has a charge of +2,

We can look up isotopic abundance for Mg and find:

A. air, B. gasoline, C. copper wire

B. Mg + O2  MgO + O C. Mg2 + O2  2 MgO D. 2 Mg + O2  2 MgO

Choice A is obviously a correct formula --- it has four hydrogen atoms

Allowed values of principal quantum number (n): positive integers

Oxoanions have names ending in “ate” or “ite”

Therefore, the correct answer is A.

Iron(III) sulfate is an ionic compound. Cation is iron(III) ion. Fe3+

Iron(III) sulfide is an ionic compound. Therefore:

QUESTION: A sample of matter is heated and found to start melting at 75.0oC. While melting, the sample temperature continues to rise to about 85.0oC.

For which pair of molecules does dipole-dipole interaction occur?

CLICK PAUSE END RECORDING

QUESTION: What is the maximum number of of electrons that can be assigned to a 2p orbital of an atom? A. 2, B. 3, C. 6, D. 10 Pauli’s Exclusion.

A. an element and two compounds, B. two elements and a compound,

Here’s a general strategy for determining empirical formulas.

X-78: mass=78.0 u, abundance = 30.0%

Sodium phosphate is an ionic compound. Cation is sodium ion. Na+

What do molecules and polyatomic ions have in common?

Potassium hydrogen phosphate is an ionic compound.

represented by a pair of filled circles,

Mole is a group count (just like dozen).

C. CaCl2(s)  Ca2+(aq) + Cl22-(aq)

K2CO3 is an ionic compound. Cation is potassium ion: K+

Which of the following is not a balanced chemical equation?

Presentation transcript:

Smallest set is obtained if greatest common factor is 1 QUESTION: What is the sum of the subscripts in the empirical formula of C6H12? A. 1, B. 2, C. 3, D. 18 Subscripts in the empirical formula = smallest set of whole numbers that reflect the relative abundance of the atoms of different elements in a compound. Smallest set is obtained if greatest common factor is 1 C-to-H ratio in C6H12 is 6:12, or 1:2 Therefore, empirical formula is CH2. Sum of coefficient in empirical formula: 1 + 2 = 3 What is the sum of the subscripts in the empirical formula of C6H12? A. 1, B. 2, C. 3, D. 18 PAUSE CLICK Empirical formula refers to a formula where the subcripts are the smallest possible whole numbers that reflect the relative abundance of the atoms of different elements in a compound. We get the smallest of whole numbers if the greatest common factor of the numbers is 1. In the case of C6H12, the carbon-to-hydrogen ratio is “six is to twelve” We can reduce this ratio to smaller whole numbers. “Six is to twelve” is equivalent to “one is to two” Therefore, empirical formula is CH2. In the empirical formula, the coefficient of carbon is 1, CALLOUT “implied 1” and the coefficent of hydrogen is 2. So, the sum of coefficient in empirical formula is 3. 1 + 2 = 3 CLICK PAUSE END RECORDING

Video ID: 4-7-2 © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08