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3 years ago

Iodine-131 decays with a half-life of 8.02

1 answer:

3 0

Radioactive material undergoes 1st order decay kinetics.

For 1st order decay, half life = 0.693/k

where k = rate constant

k = 0.693/half life = 0.693/8.02 = 0.0864 day-1

Now, for 1st order reaction,
k = $\frac{2.303}{t} X log \frac{initial.conc}{final.conc}$

Given: t = 6.01d, initial conc. = 5mg

∴0.0864 = $\frac{2.303}{6.01} X log \frac{5}{final.conc}$
∴ final conc. = 2.975 mg

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What is the ph of a solution of 0.550 m k2hpo4, potassium hydrogen phosphate?

Solnce55 [7]

We assume that we have Ka= 4.2x10^-13 (missing in the question)
and when we have this equation:
H2PO4 (-) → H+ + HPO4-
and form the Ka equation we can get [H+]:
Ka= [H+] [HPO4-] / [H2PO4] and we have Ka= 4.2x10^-13 & [H2PO4-] = 0.55m
by substitution:
4.2x10^-13 = (z)(z)/ 0.55
z^2 = 2.31x 10^-13
z= 4.81x10^-7
∴[H+] = 4.81x10^-7
when PH equation is:

PH= -㏒[H+]
= -㏒(4.81x10^-7) = 6.32

3 0

3 years ago

Condensation is a process for which a. ΔG is negative at high temperature but positive at low temperature. b. ΔH and ΔS are nega

IgorC [24]

Answer:

b. ΔH and ΔS are negative at all temperatures .

Explanation:

During the process of condensation ,

The gaseous state convert to liquid state ,

Hence , the entropy of the system reduces , i.e. , the randomness decreases .

And the value for entropy is negative ,

hence ,

Δ S = negative ,

Δ H = negative ,

Since ,

The heat is releasing from system .

hence , the most appropriate option will be ΔH and ΔS are negative at all temperatures .

7 0

3 years ago

CaCO3 For each of the following compounds, decide whether the compound's solubility in aqueous solution changes with pH. If the

Slav-nsk [51]

Answer:

Hello attached below is the data found in Aleks Data tab

answer :

i) N0

ii) N0

iii) YES , pH of highest solubility = 5

Explanation:

i) For CuBr

solubility does not change with pH hence answer = NO

ii) For MgCl2

solubility does not change with pH hence the answer = NO

iii) For Ba(OH) 2

Solubility does change with pH hence the answer = YES

and the pH at which the highest solubility will occur is = 5

attached below is the reason for the answers given

4 0

2 years ago

55 L of a gas at 25oC has its temperature increased to 35oC. What is its new volume?

ladessa [460]

Answer:

Approximately 56.8 liters.

Assumption: this gas is an ideal gas, and this change in temperature is an isobaric process.

Explanation:

Assume that the gas here acts like an ideal gas. Assume that this process is isobaric (in other words, pressure on the gas stays the same.) By Charles's Law, the volume of an ideal gas is proportional to its absolute temperature when its pressure is constant. In other words

$\displaystyle V_2 = V_1\cdot \frac{T_2}{T_1}$ ,