All categories

3 years ago

Which aqueous solution of KI freezes at the lowest temperature?

Chemistry

1 answer:

slavikrds [6]3 years ago

3 0

Answer:

b. 2 mol of KI in 500. g of water

Explanation:

We have to apply the colligative property of freezing point depression.

The formula is: ΔT = Kf . m . i

As the (Kf . m . i) is higher, then the freezing temperature will be lower.

i refers to the Van't Hoff factor (number of ions dissolved in the solution)

KI → K⁺ + I⁻ (i =2)

Kf is constant so, we have to search for the highest m (molality)

Molality means the moles of solute in 1kg of solvent.

The highest m is option b → 2 mol of KI / 0.5 kg = 4 mol/kg

a. 1 mol of KI / 0.5 kg = 2 mol/kg

c. 1 mol of KI / 1kg = 1 mol/kg

d. 2 mol of KI / 1kg = 2 mol/kg

1000 g = 1kg. In order to determine molality we need to convert the mass (g) of solvent to kg

You might be interested in

What is the half-life of a pharmaceutical if the initial dose is 500 mg and only 31 mg remains after 6 hours?

Sergeu [11.5K]

Answer:

$\large \boxed{\text{b. 1.5 h}}$

Explanation:

1. Calculate the rate constant

The integrated rate law for first order decay is

$\ln \left (\dfrac{A_{0}}{A_{t}}\right ) = kt$

where

A₀ and A_t are the amounts at t = 0 and t

k is the rate constant

$\begin{array}{rcl}\ln \left (\dfrac{500}{31}\right) & = & k \times 6\\\\\ln 16.1 & = & 6k\\2.78& =& 6k\\k & = & \dfrac{2.78}{6}\\\\& = & 0.463 \text{ h}^{-1}\\\end{array}$

2. Calculate the half-life

$t_{\frac{1}{2}} = \dfrac{\ln2}{k} = \dfrac{\ln2}{\text{0.463 h}^{-1}} = \textbf{1.5 h}\\\\ \text{The half-life is $\large \boxed{\textbf{1.5 h}}$}$

4 0

3 years ago

Which of the following is not a conjugate acid-base pair?

-Dominant- [34]

Answer:

A. H3O+/OH−

Explanation:

A conjugate acid-base pair are a pair of molecules that differ in 1 H⁺

A. The conjugate pair of H₃O⁺ = H₂O not OH⁻

B. The conjugate pair of NH₄⁺ is NH₃

C. The conjugate pair of C₂H₃O₂⁻ is HC₂H₃O₂

D. The conjugate pair of H₂SO₃ is HSO₃⁻

That means right option, that is not a conjugate acid-base pair, is:

5 0

3 years ago

Thomas has 235 grams of K2S in the chemistry lab. How many atoms of potassium (K) are in 235 grams of the compound?

iVinArrow [24]

The number of atoms of K that are in 235 g of the compound is

2.57 x10^24 atoms

calculation

Step 1: find the moles of K2S

= moles = mass/molar mass

= 235 g/110 g/mol= 2.136 moles

Step 2: multiply 2.136 moles by no. of K atoms in K2S

= 2.136 x2 = 4.272 moles

Step 3: use the Avogadro's law to determine number of K atoms

that is according to Avogadro's law 1 mole = 6.02 x 10^23 atoms

4.272 moles= ? atoms

by cross multiplication

= (4.272 moles x 6.02 x10^23 atoms) / 1 mole = 2.57 x10^24 atoms

4 0

3 years ago

Which statement describes clean air as a natural resource? Select three options.

Mumz [18]

Answer:

a,d,e

Explanation:

its a,d, and e because clean air keeps us alive and other organisms need it to stay alive

6 0

3 years ago

Read 2 more answers

Speed is the ratio of the distance an object moves from a reference point to

Vladimir [108]

The correct option is A.

Speed is the ratio of the distance an object moves from a reference point to the amount of time it takes to travel the distance.

For a fixed distance, if the time required to travel the distance is less than the speed is high. However, if time to cover the same amount of distance is more than the speed is low. Therefore, the measurement of speed distance and time has an inverse relationship.

4 0

2 years ago