25.00 ml of 0.500 M Na2CO3 at 20.00 ℃ is mixed with 29.00 ml of 0.600 M HCl, in a coffee-cup calorimeter at 20.00 ℃. After stirring and allowing the reaction to go to completion, the final temperature is 26.50 ℃. As the gaseous CO2 forms from the reaction under constant atmospheric pressure of 0.988 atm, the volume changes by 2.6 L per 1 mol of CO2. Assume the final solution has the density of 0.982 g mL and specific heat capacity of 4.184 J g • ℃ . Calculate the change in internal energy ΔE, of the reaction (in kJ mol).

answer carbon and three oxygen atoms;

answer: atomic mass was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

explanation:

originally atomic mass was used to arrange elements on the periodic table from left to right in a row. each column then shows similar properties of elements of a group.

in modern periodic table, the atoms are arranged in increasing atomic number. as atomic number represents the number of protons in an atom which is unique for every atom.  

the answer is 2-methylbutane. i just took a quiz and i got it wrong and this is what my teacher sai the correct answer was.