In the reaction c + o2 → co2, 18 g of carbon react with oxygen to produce 72 g of carbon dioxide. what mass of oxygen would be needed in the reaction? 18 g 54 g 72 g 90 g

The answer to your question is: 54 g

Explanation:

Reaction

                                C  + O₂   ⇒   CO₂

Carbon mass = 18 g

Carbon dioxide mass = 72 g

To solve this question, we must remember the Lavoisier law of conservation of mass, that states that in an isolated of closed system, matter can not be created or destroyed.

This law states that the mass of the reactans must be equal to the mass of the products.

Then

Mass of reactants = 18 + ?

Mass of products = 72

So,

                  18 + x = 72

                  x = 72 - 18

                x = 54 g of oxygen                    

when 25.0 ml of 0.700 mol/l naoh was mixed in a calorimeter with 25.0 ml of 0.700 mol/l hcl, both initially at 20.0 °c, the temperature increased to 22.1 °c. the heat capacity of the calorimeter is 279 j/°c.

the equation for the reaction is:

naoh + hcl → nacl + h₂o

moles of hcl = 0.0250 l hcl ×

0.700

mol hcl

1 l hcl = 0.0175 mol hcl

volume of solution = (25.0 + 25.0) ml = 50.0 ml

mass of solution = 50.0 ml soln ×

1.00

ml soln

= 50.0 g soln

δt=t2-t1

= (22.1 – 20.0) °c = 2.1 °c

the heats involved are

heat from neutralization + heat to warm solution + heat to warm calorimeter = 0

q1+q2+q3=0

nδh+mcδt+cδt=0

0.0175 mol ×

δh

+ 50.0 g × 4.184 j·g⁻¹°c⁻¹ × 2.1 °c + 279 j°c⁻¹ × 2.1 °c = 0

0.0175 mol ×

δh

+ 439.32 j + 585.9 j = 0

0.0175 mol ×

δh

= -1025.22 j

δh=1025.22j0.0175 mol= -58 600 j/mol = -58.6 kj/mol

answer; talc and gypsum;