It would be Microwaves. The cosmic microwave background (CMB, CMBR), in Big Bang cosmology, is electromagnetic radiation as a remnant from an early stage of the universe, also known as "relic radiation".

8 0

3 years ago

alculate the standard enthalpy of formation of ethanoic acid given that the standard enthalpy of combustion for carbon is –394 k

agasfer [191]

Answer:

The standard enthalpy of formation of ethanoic acid is -484 kJ/mol.

Explanation:

$C(g)+O_2(g)\rightarrow CO_2(g),\Delta H_{1, comb}=-394 kJ/mol$ ...[1]

$H_2(g)+\frac{1}{2}O_2(g)\rightarrow H_2O(l),\Delta H_{2, comb}=-286 kJ/mol$ ..[2]

$CH_3COOH(l)+2O_2(g)\rightarrow 2CO_2(g)+2H_2O(l),\Delta H_{3, comb}=-876 kJ/mol$ ..[3]

The standard enthalpy of formation of ethanoic acid :

$2C(g)+2H_2(g)+O_2(g)\rightarrow CH_3COOH, \Delta H_{4}=?$ ..[4]

Using Hess's law to calculate :

2 × [1] + 2 × [2] - [3] = [4]

$\Delta H_4=2\times (-394 kJ/mol)+2\times (-286 kJ/mol) - (-876 kJ/mol)$

$=\Delta H_4=-484 kJ/mol$

The standard enthalpy of formation of ethanoic acid is -484 kJ/mol.

5 0

3 years ago

A chemist adds of a sodium thiosulfate solution to a reaction flask. Calculate the mass in grams of sodium thiosulfate the chemi

schepotkina [342]

This is a incomplete question.The complete question is:

A chemist adds 180.0 ml of a 1.77 mol/L of sodium thiosulfate solution to a reaction flask. Calculate the mass in grams of sodium thiosulfate the chemist has added to the flask. Be sure your answer has the correct number of significant digits.

Answer: 50.4 g

Explanation:

To calculate the number of moles for given molarity, we use the equation:

$\text{Moles of solute}={\text{Molarity of the solution}}\times{\text{Volume of solution (in L)}}$ .....(1)