Preparas una solución 0.25 m de NaOH, si tomas una muestra de 30 ml de esta solución y lo llevas a un aforo de 500 ml ¿cuál será su pH y su pOH final?

pOH = 1.82

pH = 12.18

Explanation:

pH is defined as - log [H⁺] while pOH is defined as - log [OH⁻]

When you take 30mL of a solution 0.25M of NaOH and complete to 500mL the concentration of NaOH is:

0.25M of NaOH ₓ (30mL / 500mL) = 0.015M of NaOH. As NaOH is a strong base and dissociates completely, the concentration of OH⁻, [OH⁻] is  0.015M. Thus, pOH is:

pOH = - log [0.015M] = 1.82

As 14 = pOH + pH, pH of the solution is:

pH = 14 - 1.82

pH = 12.18

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.