Science Reaction Study guide
In the equation 2Na + 2H2O ———> 2NaOH + H2, 46 grams of sodium Na reacted with 36 grams of water H2O. If 2 grams of hydrogen gas H2 is produced by this reaction, what is the mass of sodium hydroxide NaOH produced?
80 grams
Chemical reactions are represented by sentences known as?
Chemical equations.
Clues to a Chemical Reaction?
Color change, formation of a solid (ppt), formation of a gas (bubbles), heat and/or flame is produced or absorbed.
What are the indications that a chemical reaction has taken place?
Color change, formation of precipitate, formation of a gas, odor change, temperature change.
Chemical equation shows _______________before a chemical reaction takes place on the left ________________and compounds formed from the chemical reaction on the right___________?
Compounds, reactants, products.
Chemical equation?
Describes exactly what happens in a chemical reaction.
Aq?
Dissolved in water (aqueous solution)
During chemical reactions the process ALWAYS involves?
Energy
G?
Gas
A student asks why the ashes from a fire have a much lower mass than the wood that was burned?
Gases are released into the air.
The mass of a rusty bicycle is found to be slightly greater than the mass of the same bicycle before it rusted. The change in mass indicates that the rusting process?
Involves metal bonding with other atoms.
Chemical reaction?
Is a process in which one or more substances are converted into new substances with different physical and chemical properties.
L?
Liquid
Physical change example?
Melting ice, tearing paper, splitting wood, mixing a cake.
A decomposition reaction starts with one______________?
One reactant and ends up with two or more products. EX: NaCl ——-> Na + Cl 2
Chemical change?
Produces one or more new substances with new properties, characteristics, etc....the new substance can no longer be returned to its original form.
A synthesis reaction starts with two______________?
Reactants and ends up with one product. Ex: Na + Cl 2 —-> NaCl
A combustion reaction is when the _________?
Reactants are oxygen and a hydro carbon and the products are water (H2O) and carbon dioxide (CO2). Ex: CH4 + 2O 2——-> CO2 + 2H2O
Chemical reactions involves a ______________of the ways in which atoms are grouped. The atoms form bonds to become more stable (set of 8). __________________usually result?
Rearrangement, new molecules
Exothermic?
Refers to a reaction where energy (as heat) flows from the system (HOT)
Endothermic?
Refers to a reaction where energy (as heat) flows into system (COLD)
Physical change?
Retain original properties, characteristics, etc...appearance may change but NOT the properties.
Chemical change example?
Rusting iron, burning wood or paper, cooking an egg, baking a cake.
The physical states of the reactants and the products are indicated by using what symbols?
S, l, g, aq, ——>
S?
Solid
Law of Conservation of mass states?
That mass can neither be created nor destroyed in a chemical or physical reaction. So, the amount of matter stays the same. Ex: 3AB2 ——-> 3A + 6B
If all the reactants in a chemical reaction are completely used, which of the following statements accurately describes the relationship between the reactants and the products?
The total mass of the reactants must equal the total mass of the products.
What would support the idea that mass is conserved in a reaction that produces a gas as a product?
Trapping the gas and measuring its mass.
A double replacement reaction starts with ___________?
Two reactants and ends up with two products. In this case both reactants are compounds and both products are compounds. Ex: NaOH + HCl ———> HOH + NaCl
A single replacement reaction starts with______________?
Two reactants and ends up with two products. The uncombined element takes the place of the combined element in the compound. EX: K + AgCl 2 ——-> Ag + KCl
During chemical reactions atoms have the opportunity to obtain a complete set of ______________and become more stable. Old bonds are broken, new bonds are formed and atoms are ________________?
Valence electrons, rearranged.
——-> ?
Yields
Reactants ——-> Products. The arrow in the equation is read as?
Yields or produces.
The reaction below shows potassium oxide being produced KO2 by combining oxygen O2 with potassium K. The mass of potassium is 50 grams and the mass of oxygen is 12 grams. What is the mass for the potassium oxide that was produced?
62 grams
According to the law of conservation of mass, how much zinc was present in the zinc carbonate? Calcium 64g, zinc carbonate 192g yields ——-> calcium carbonate 152g and zinc ?
104 grams
Students have two identical beakers with a mass of 20 grams each. The students pour a different liquid reactant into each beaker. The total mass of the two beakers with the reactants is 50 grams. Next, the students combine Reactant 1 and Reactant 2 into one of the beakers. A chemical reaction produces a product. If all the reactants are consumed and no gases are produced, what is the total mass of the product in one beaker?
50 grams
