Chemical Rxns Flashcards
When filling up an atom’s electrons into the energy levels/ shells, how should you go about it?
- look at the atomic #= the number of protons , which in a neutral atom is equal to the number of electrons
- look at the rows aka periods to see the number of energy levels/ shells
- look at the columns aka the groups to see the number of valence electrons
- place the said number of valence electrons into the outermost/ valence shell
- fill in the other electrons into the electron levels/ shells via the 2, 8, 18, 32, 50 rule
Valence electrons are found where? What do they participate in?
- in the outermost, valence shell
- they are the ones participating in the chemical bonds
The number of valence electrons tells us what?
how the atom will react with other atoms
What do all atoms strive to fullfill what rule? What does that rule dictate?
- octet rule
- the atom strives to have 8 electrons in its valence/ outermost shell through losing, gaining , or sharing the valence electrons , with the goal of becoming like its nearest noble gas
What is the max electrons supported by each energy level (up to 5)?
- 2
- 8
- 18
- 32
- 50
examples in ipad chemical reactions sheet
How do you find out how many bonds an atom will make?
easy: number in the ionic charges formed by the element
based on how many electrons are gained or lost to become its nearest noble gas (aka the way to get to its ionic charge)
What is a chemical bond?
atoms gaining or losing or sharing valence electrons to satisy the octet rule, which is to get 8 electrons in the valence/ outermost shell of the atom to become like its nearest noble gas
In general, what are the 3 types of chemical bonds?
- ionic
- covalent
- hydrogen
Describe ionic bonds
* atoms that are involved do what?
* what type of elements form these bonds?
* explain the EN difference b/w the atoms invovled
* what are some examples (5)?
- atoms invovled will either gain or lose electrons (transfer of electrons from metal to nonmetal) to generate ions (anions or cations) that have a bond through just attraction b/w opposite charges
- b/w metal (less EN –> lose electrons to become a cation) and nonmetal (more EN –> gain electrons to become an anion)
- LARGE EN difference b/w atoms invovled
examples
* NaCl , NaBr, KCl
* MgO
* CaS
picture examples in ipad chemical reactions
Describe covalent bonds
* atoms that are involved do what?
* what type of elements form these bonds?
* what are the 2 types of covalent bonds?
* what are some examples (general, polar, nonpolar)?
- atoms involved are sharing electrons (sometimes one atoms is more EN than the other, so attracts more e-‘s and is partially - and the other is partially +)
- b/w 2 nonmetals
- polar and nonpolar
Examples
* in general: CO2
* polar: HCl, OH, H2O (dipole moment pointing towards the more EN atom ie. O in H2O)
* nonpolar: diatomic mlcs and C-H bonds
picture examples in ipad chemical reactions
Explain polar bonds (including what type of bond it is, including examples)
- a type of covalent bond where the EN difference b/w the two atoms are greater than or equal to 0.5 –> so there is an unequal sharing of electrons with one atom being more EN and attracting more electrons and being partially negative and other one being partially += forming a dipole moment, which points towards the more EN atom)
Examples
* HCl (H is partially +, Cl is partially -)
* OH (H is partially +, O is partially -)
* H2O (H is partially +, O is partially -)
Explan nonpolar bonds (including what type of bond it is, including examples)
- a type of covalent bonds where the EN difference b/w the two atoms is less than 0.5 –> so there is an equal sharing of electrons
Examples
* diatomic mlcs and C-H bonds
Describe hydrogen bonds
* what elements form these bonds?
* where are these bonds found?
* strength of them compared to ionic/ covalent bonds
- H-NOF
- found in H2O, proteins, nucleic acids (DNA); found within a single mlc OR b/w mlcs
- weaker than ionic and covalent bonds and are NON-covalent
Chemical reactions are depicted by what?
chemical equations
Describe chemical reactions
* what turns into what?
* what law does it follow?
- one or more substances turns into a completely new substance
- law of conservation of mass : DOES NOT create or destroy mass or the atoms –> which means the number of atoms aka the number of moles of element is the SAME on the reactants and products side
What is the number of moles represented in in an equation
the coefficient before the element
Chemical reactions balancing practice in ipad chemical reactions document
In general, what are the 5 types of chemical reactions?
- combination/ synthesis
- decomposition
- single displacement aka single replacement and single substitution
- double displacement aka double replacement and substition and precipitation rxn
- combustion
Explain combination reaction (including what is another name for it)
- aka synthesis reaction
- 2 reactants combine to form 1 product (A + B –> AB) [ element + element –> cmpd]
Examples in ipad
Explain decomposition reaction
- usually endergonic, so requires energy
- 1 reactant breaks down into 2 or more products (AB –> A + B) [ cmpd –> element + element]
examples in ipad
Explain single displacement rxn (including what is another name for it)
- single replacement or single substitution rxn
- 1 reactant is replaced or displaced with another ( A + BC –> B + AC OR C + AB) [ element + cmpd –> element + cmpd]
examples in ipad
Explain double displacement rxn (including what is another name for it)
- double replacement and substitution and precipitation rxn
- 2 compounds come together to form two other compounds with 2 element swapped; solid made is the precipitate ( AB + CD –> AD + CB) [ cmpd + cmpd –> cmpd + cmpd]
examples in ipad
Explain a combustion reaction (including is it exo or endothermic)
a substance reactions with O2 to release energy (exothermic) as light and heat ( O2 + _____ –> CO2 + H2O)
What are the factors that influence the rate of a reaction? Explain each
- catalyst : lowers the activation energy, which is the min energy to start a chemical reaction, which increases the rate of the reaction
- concentration : inc the conc of reactant = inc the number of collisions b/w them = inc rate of rxn
- temperature: inc the temp = inc the frequency and speed of collisions and also the KE of the reactants –> more fraction of reactants are able to reach the AE –> more reactants are able to complete the rxn
- pressure (only applies to gasesous atoms): inc pressure , increases the temperature = increases the OVERALL velocity of the particles –> inc the # if collisions –> inc rate of rxn
- SA: inc SA b/w reactants –> inc the # if collisions –> inc the rate of rxn
What item are catalysts usually? What macromolecule is that item usually? Give an example of that item. Give one characteristic.
- enzymes
- proteins (end in -ase)
- amlyase turning amylose (starch) into maltose (simple sugar)
NOT consumed in a reaction
Explain Le Chatelier’s Principle
- when a stressor is added to a system, will try to shift to offset the stressor or to restore the chemical equilibrium
What are examples of stressors dictated by Le Chatelier’s Principle
- change in temp (inc or dec) (factor in endothermic = heat is reactant or exothermic (heat is product) (also inc in temp in general will inc the OVERALL velocity of the particles = inc the number of collisions = inc rate of reaction)
- change in concetration of reactions or products (inc or dec)
- change in pressure (only when dealing with gases and when there is an actual DIFF in moles of gas b/w reactants and products)- a inc in pressure shifts the reaction towards the side with less moles of gas and a dec in pressure shifts the reaction towards the side with more moles of gas
examples in ATI manual page 242 question 1 and 2.
Extra:
What is a neutralization reaction?
- acid + base –> salt (ionic cmpd) + water
examples in ipad
What subtance lowers the activation energy of a chemical reaction?
catalyst (most of the time an enzyme, which are usually proteins)
An enzyme does what to a chemical reaction?
speed up the forward AND reverse reaction
Extra:
What is a redox reaction?
OIL RIG
* oxidation has electrons as product and reduction has electrons as reactant
What are two elements that DO NOT follow the octet rule? Instead what rule do they follow? What does that rule say?
- H and He
- DUET rule
- need 2 electrons in valence/ outer shell instead of 8.
What elements should be balanced last?
O and H
