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Counting Atoms/Conservation of Mass

Total questions: 39

Worksheet time: 52mins

Name
Class
Date
1.
How many Hydrogen are in 4H2O?
a)
6
b)
8
c)
2
d)
4
2.
How many Oxygen are in H2O?
a)
1
b)
2
c)
0
d)
4
3.
How many Magnesium are in 10MgCl2?
a)
10
b)
5
c)
20
4.
2H2 + O2 ----> 2H2O What is the product?
a)
------>
b)
2H2O
c)
2H2+ O2
5.
2H2 + O2 --------> 2H2O What  are the reactants?
a)
----->
b)
2H2O
c)
2H2 +O2
6.
2H2 + O2 ----> 2H2O What is the product?
a)
------>
b)
2H2O
c)
2H2+ O2
7.
2H2 + O2 --------> 2H2O What  are the reactants?
a)
----->
b)
2H2O
c)
2H2 +O2
8.
How many O's are in Al₂(SO₄)₃
a)
4
b)
12
c)
7
d)
24
9.
Number of H in 3(NH₄)₂CrO₄
a)
4
b)
2
c)
8
d)
24
10.
How many atoms are there TOTAL in:
H2SO4
a)
6
b)
5
c)
7
d)
3
11.
How many elements are in C6H12O6?
a)
1
b)
2
c)
3
d)
4
12.
How many Sodium (Na) are in 6NaCl?
a)
1
b)
12
c)
6
13.
Number of N in (NH₄)₂CrO₄
a)
1
b)
2
c)
8
d)
16
14.
A subscript is the small number below a(n) ________ that tells the number of _______ of that element.
a)
element symbol; atoms
b)
atom; element symbol
c)
subscript; protons
d)
compound; elements
15.
How many O's are in Al₂(SO₄)₃
a)
4
b)
12
c)
7
d)
24
16.

How many atoms of Iron in the following equation?

C2HAu5

a)

2

b)

0

c)

9

d)

7

17.

How many total atoms in the following equation?

2(H2)3

a)

2

b)

6

c)

7

d)

12

18.

In the chemical formula C12H22O11C_{12}H_{22}O_{11}  , how many elements are there?

a)

1

b)

2

c)

3

d)

4

19.

How does a balanced chemical equation satisfy the Law of Conservation of Mass?

a)

During a chemical reaction, matter is destroyed.

b)

During a chemical reaction, the total number of atoms increases.

c)

 During a chemical reaction, one or more new substances are formed.

d)

During a chemical reaction, the total amount of matter stays the same.

20.

In a chemical reaction, the number of atoms in the products will always equal which amount?

a)

the number of atoms in the reactants

b)

half of the number of atoms in the reactants

c)

twice the number of the atoms in the reactants

d)

thrice the number of the atoms in the reactants

21.

Jin bought a heat pack that weighs 15 g. He shook it so it would release heat to warm his hands. The release of heat indicates a chemical reaction took place in a closed system. What would be the mass of the heat pack after the chemical reaction?

a)

5 g

b)

10 g

c)

12 g

d)

15 g

22.
Maria fills a bowl with 200 g of water. She puts the bowl of water in the freezer, and the water freezes. Which will most likely be the mass of the frozen water?
a)
50 g
b)
100 g
c)
200 g
d)
400 g
23.
What will weigh more when a chemical change is complete?  The reactants before the chemical reaction, or the product after the reaction is complete?
a)
They both will weigh the same
b)
The product always weighs more than the reactant
c)
The reactant will weigh more than the product
d)
They both will loose mass after the reaction
24.
If a reaction starts with a total 75g of reactants it should produce 
a)
a total of 40g of products
b)
a total of 75g of products
c)
a total of 180 g of products
d)
None of the above
25.
In the reaction AB-----> A + B reactant AB has 12g and product B has 5g. How many grams should product A have?
a)
17g
b)
2g
c)
7g
d)
None of the above
26.
12g of Carbon react with 16g of Oxygen, how much carbon monoxide (CO) is formed? 
a)
28 g
b)
4g
c)
30g
d)
12g
27.

32 g of Oxygen completely reacts with 8 g of Hydrogen to produce _____ g Water

a)

8

b)

12

c)

24

d)

40

28.

4 grams of hydrogen and 32 grams of oxygen will combine to form:

a)

36 grams of water

b)

28 grams of hydroxide

c)

32 grams of oxygen

d)

36 grams of deuterium

29.

In a chemical reaction, 4 grams of sodium must combine with how many grams of chlorine to produce 10 grams of table salt?

a)

4 grams

b)

6 grams

c)

8 grams

d)

10 grams

30.

Why does this picture demonstrate the Law of Conservation of Mass?

a)

the number of atoms of each element are the same on both sides

b)

they start out separate and end up combined

c)

the same elements are used

d)

it doesn't demonstrate the Law of Conservation of Mass

31.

When a log is burned, what happens to the wood?

a)

The mass stays the same, but becomes smoke and ash.

b)

It disappears.

c)

The mass changes as it goes away.

d)

Nothing. You're imagining things.

32.
Balance this equation-
__P4 + __O2 --> __P2O3
a)
it is already balanced
b)
2, 1, 3
c)
1, 2, 3
d)
1, 3, 2
33.
 Mg  +  ___ HCl  →   MgCl2  +   H2
a)
1
b)
2
c)
3
d)
4
34.
When CaCO3 is heated, it forms CaO and CO2. Which of these statements best describes the mass of the products if 100 g of CaCO3 is heated?
a)
The difference in the products’ masses is equal to the mass of the CaCO3
b)
The sum of the products’ masses is less than the mass of the CaCO3
c)
The mass of each product is equal to the mass of the CaCO3
d)
The sum of the products’ masses equals the mass of the CaCO3
35.
Students react baking soda & vinegar.
Which of the following would provide the evidence that the number of atoms present before a chemical reaction is equal to the number of atoms present after the chemical reaction?
a)
The mass of the plastic bag, baking soda, and vinegar before the reaction was equal to the mass after the reaction.
b)
Bubbles were produced during the reaction, which meant that a gas was being produced.
c)
The plastic bag did not change in any way, indicating that it was not involved in the reaction.
d)
The mass of the baking soda was exactly equal to the mass of the vinegar used to create the chemical reaction.
36.
24 g of magnesium reacts with 38 g of fluorine to produce _____ g magnesium fluoride
a)
62 
b)
38
c)
24
d)
14
37.
Bob puts 200 grams of ice into a pitcher with 900 grams of water. He gets distracted and comes back later to find that the ice has melted in the water. How many grams of water does Bob now have in the pitcher?
a)
200 g
b)
700 g
c)
1,100 g
38.
Which Chemical Equation is Balanced?
a)
CH₄+O₂------CO₂+2H₂O
b)
H₂+O₂-----2H₂O₄
c)
4Al+3O₂-----2Al₂O₃
39.
Is this equation balanced or unbalanced? 
2Fe2O3 + 3C --> 4Fe + 3 CO2
a)
balanced
b)
unbalanced

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