Question

Which statement is a correct expression of the Law of Conservation of Mass?

A.
The total mass is unpredictable in a chemical reaction.

B.
The total mass remains the same during a chemical reaction.

C.
The total mass decreases during a chemical reaction.

D.
The total mass increases in a chemical reaction.

Answer 1

What do you think? "Conservation of Mass" what might be the most reasonable answer?

Answer 2

d

Answer 3

If the mass increase it wouldn't be conserved. When something is conserved it is protected, remaining constant. So try again. :)

Answer 4

b

Answer 5

Exactly :)

Answer 6

help me with 4 more please

Answer 7

Which element(s) are not balanced in this equation?

Fe2O3 + 3 CO → Fe + 3 CO2

A.
Only the Fe is unbalanced.

B.
Only the O is unbalanced

C.
Fe and O are both unbalanced.

D.
C and O are both unbalanced

Answer 8

I think the rules of OS requires you to open a new question, but as it does not really matter to me lets fast look at it.

Lets look at the obvious:
We got iron (Fe), oxygen (O) and carbon (C) in the equation.
There has to be the same amount on each side of the equation [also according to the conservation of mass ;)]
So try give a shot, what element(s) are unbalanced?

Answer 9

d

Answer 10

Okay, not exactly correct. Lets count the atoms on both sides together.
Are you familiar with the terms reactants and products?

Answer 11

no

Answer 12

b right

Answer 13

Okay so lets fast get some notation out of the way, when we talk about a chemical reaction we usual say:
Reactants -> products.
So in your case iron(III) oxide (Fe2O3) and carbon monoxide (CO) are the reactants, and the rest are products.
So lets count how many on the reactant side:
Fe: 2
O: 3+3=6
C: 3

Try do the same for the products.

Answer 14

Currently it seems to me you guess, so I think it is best we develop a method to which you can solve questions like this and get a understanding of it.

Answer 15

so it is c ok right

Answer 16

Are you absolutely sure? I still suggest you try write down the amount of atoms in the products.

Answer 17

is it a

Answer 18

Yes it is
Products:
Fe: 1
O: 2*3=6
C: 3

So to balance it we write instead
Fe2O3 + 3 CO -> 2 Fe + 3 CO2

But you are obviously guessing, if you come to a exam or test in this, how would you stand chance?

Answer 19

stand a chance*

Answer 20

the answer is a

Answer 21

4 more eh?