What elements do water, carbon dioxide, and rust have in common

                     The common element is Oxygen.

Explanation:

                    In order to find out the common elements between water, rust and carbon dioxide we will first write down the chemical formulas of these compounds.

                (i) Water  =  H₂O

                                           Each water molecule is made up of two atoms of hydrogen and one atom of oxygen.

                (ii) Carbon Dioxide  =  CO₂

                                            Carbon dioxide is made up of one atom of carbon and two atoms of oxygen.

                (iii) Rust =  Fe₂O₃

                                             Rust is formed when Fe (Iron) is oxidized. Hence, it is made up of two iron atoms and three oxygen atoms.

Conclusion:

                  Hence, Oxygen is the only common element found in all these three compounds.

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