Multiple choice questions...?

Question

1. Which of the following statements, comparing the products of any chemical reaction with reactants, is true?
a) There are always as many molecules after the reaction before.
b) Their total number of moles is always the same
c) Their total mass is always the same
d) The products always possess the same amount of energy as the reactants.

2. For the reaction Ng(g)+3H2(g) -(to, should be arrow) 2NH3(g), the total mass of products divided by the total mass of reactants is
a) 2.00
b) 0.25
c) 0.50
d) 1.00

3. Carnon monoxide burns in oxygen according to the equation
2CO(g) + O2(g)- (arrow sign) 2CO2(g)
The number of moles of oxygen required for the combustion of 28g og carbon monoxide is
a) 2.00
b) 1.00
c) 0.50
d) 0.25

Thankyou for helping. Please help chemistry wizzes. Please be 100% sure of your answers.

Answer 1

1.) Mass is neither created nor destroyed in a chemical reaction. The total mass of all reactants is equal to the total mass of all products. The answer is c.

2.) d. each side of the arrow has the same total mass.

3.) The number of moles in 28 g of CO is

28 g / 28 g/mole = 1.00 mole

From the equation, 1 mole of CO needs 1/2 mole of O2. The answer is c.

Answer 2

1. a
2. d
3. b