Acertain substance x has a normal boiling point of 124.2 °c and a molal boiling point elevation constant k,-06-0c-kg-mol ·a solution is prepared by dissolving some urea ((n112)co) in 650. g ofl. this solution boils at 124.7 oc, calculate the mass of urea that was dissolved. be sure your answer has the correct number of significant digits. 31.48 g

32 g

Explanation:

The increase in the boiling point of X can be calculated using the following expression.

ΔT = Kb × b

where,

ΔT: increase in the boiling point

Kb: molal boiling point constant (0.62 °C.kg/mol) (I looked it on the web)

b: molality of the solute

ΔT = Kb × b

(124.7°C - 124.2°C) = (0.62 °C.kg/mol) × b

b = 0.81 mol/kg

The mass of X is 650 g (0.650 kg). Then, the moles of urea (solute) are:

The molar mass of urea is 60.06 g/mol. The mass of urea is:

when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.

i'm assuming that the correct answer is indeed the first one/ "a"..