Lesson chem equations & chem reactions

Multiple Choice

Which of the following is an example of a chemical change?

• Melt ice

• Dissolve sugar in water

• Burn a piece of wood

• Boil water

• crush ice

Key words

chemical changes
combust, burn, ferment, tarnish, corrode, rust, oxidize, neutralize, react with, digest, rot, decompose

physical changes
dissolve,
any change in state (phase) like boil or condense or evaporate or melt or freeze,
cut or slice or crush or trim

Dropdown

Dissolving ​

Select answer

corroding or tarnishing​

Select answer

Multiple Choice

Which of the following best describes a chemical reaction?

• A process where substances are physically mixed together

• A chemical change where reactants are transformed into different products

• A process where substances are separated by physical means

• changes in state like boiling, evaporating, melting, freezing, condensing

• dissolving, crushing, trimming

Match

Match the following

• reactants

• products

• coefficients

• subscripts

• yields sign

present at start of reaction

newly made at end of reaction

of each type of reactant or product

atoms inside one molecule

arrow separating reactants & products

• present at start of reaction

• newly made at end of reaction

• of each type of reactant or product

• atoms inside one molecule

• arrow separating reactants & products

Multiple Choice

Which one of these is NOT evidence that a chemical change has occurred after two compounds are mixed together.

• compounds dissolve

• gas bubbles form

• color changes

• new solid (precipitate) forms

• temperature changes a lot

Multiple Choice

If a chemical equation describes a chemical change, then the chemical formulas of reactants are ALWAYS DIFFERENT from the chemical formulas of products.

• true

• false

Multiple Choice

Which of the following statements about reactants and products in a chemical reaction is correct?

• Reactants are formed (made) ; products are destroyed (used up)

• Reactants are used up (altered); products are formed

• reactants & products have the same chemical formulas

• products are always bigger than reactants

Multiple Choice

True or False. During a chemical change, atoms are rearranged as old bonds are broken and new bonds are made

• true

• false

Dropdown

the law of conservation of mass states that the total mass of the reactants must be ​

Select answer

the total mass of the products. Matter (atoms) are not created or destroyed, but they may​

Select answer

​

Multiple Select

Which of the following are true about coefficients and subscripts in a chemical equation?

• Coefficients are in front of a chemical formula & on the line

• Subscripts are written inside chemical formulas & under the lines

• Coefficients tell you how many molecules are present

• a subscript shows the # atoms of the left element

• all of these are true

Math Response

According to the law of conservation of mass, if 3.0 g and 5.9 g of reactant are used, then what mass of product is formed?_._g

Type answer here

Correct Answer: 8.9

Deg^°

Rad

Math Response

If 15.0 g products are made from two reactant and if one of those had a mass of 10.0 g, then what is the mass of the other reactant?_._g

Type answer here

Correct Answer: 5.0

Deg^°

Rad

Multiple Choice

What is the coefficient of carbon dioxide in this balanced equation?

• 1

• 2

• 3

Multiple Choice

What is the subscript of in H in the dihydrogen monoxide product in this balanced equation?

• 1

• 2

• 3

• 4

Multiple Select

When is the law of conservation of mass obeyed? Choose 2.

• when a chemical equation is balanced

• when all atoms are equal in #s in reactants & product

• when reactants & products have the same formulas

• When none of the reactant is used up.

Multiple Select

Select three correct rules for counting atoms in a chemical formula.

• Coefficients go to the entire compound.

• Subscripts affect only the element to the left of the subscript.

• Subscripts propagate through parentheses if to the right of them.

• Coefficients and subscripts are added together.

Multiple Choice

Which one of the following statements about subscripts and coefficients is correct?

• Subscripts apply to the entire compound.

• Coefficients only affect the element immediately to their right.

• Coefficients apply to the entire compound, while subscripts only affect the element to their left.

• Subscripts and coefficients are interchangeable.

Al 3 x 2 = 6
S 3 x 1 x 3 = 9
O 3x 4 x 3 = 36

3Al₂(SO₄)₃

Cu 1 x 1 = 1
N 1 x 1 x 2 = 2
O 1 x 3 x 2 = 6

Cu(NO₃)₂

When a compound chemical formula contains parentheses, a subscript is distributed to all atoms inside the parentheses.

Math Response

How many O atoms on the reactants side of this chemical equation? Cu + 2AgNO₃ --> Cu(NO₃)₂ + 2Ag

Type answer here

Correct Answer: 6

Deg^°

Rad

Math Response

How many O atoms on the products side of this chemical equation? Cu + 2AgNO₃ --> Cu(NO₃)₂ + 2Ag

Type answer here

Correct Answer: 6

Deg^°

Rad

Math Response

What is the subscript of N in 2AgNO₃ ?

Cu + 2AgNO₃ --> Cu(NO₃)₂ + 2Ag

Type answer here

Correct Answer: 1

Deg^°

Rad

Multiple Choice

What is the coefficient of product lead iodide?

H₂O(l) +PbCO₃ (aq) + 2AgI (ag) --> PbI₂(s) + Ag₂CO₃(aq) + H₂O(l)

• 1

• 2

• 3

• 4

Multiple Choice

Which is a solid?

H₂O(l) +PbCO₃ (aq) + 2AgI (ag) --> PbI₂(s) + Ag₂CO₃(aq) + H₂O(g)

• reactantPbCO₃

• reactant PbI₂

• product PbI₂

• H₂O

Multiple Choice

Which of the following statements is correct according to the rules for balancing chemical reactions?

• change coefficients but not subscripts.

• change subscripts but not coefficients.

• change both coefficients & subscripts.

• You cannot change any #s in the equation

Fill in the Blank

Fill in the blank: In balancing chemical equations, you can change the ___ but never the subscripts.

Multiple Choice

Which of the following is an example of a physical change based on the experiments shown?

• Mixing two clear liquids to form a white solid (Station 5)

• Burning a strip of magnesium (Station 2)

• Dissolving a solid in water (Station 9)

• A glowing flask (Station 4)