A solubility curve tells you the minimum temperature needed to dissolve an amount of solute.

A 1.11 g sample of caffeine, C8H10N4O2, burns in a constant-volume calorimeter that has a heat capacity of 7.85 kJ/K. The temper

VladimirAG [237]

Answer:

401135 kJ

Explanation:

From the balanced quation,

(q/n) = CΔE

Molar heat of combustion = 7.85kJk × (303.81-298.70)k

= 7.85kj × 5.11

= 40.1135kj

4 0

2 years ago

The ΔHvap of a certain compound is 49.09 kJ·mol–1 and its ΔSvap is 53.69 J·mol–1·K–1. What is the boiling point of this compound

rusak2 [61]

Hey there !

Convert Joule to KJ :

1 j ---------------- 0.001 kj
53.69 j ----------- Kj

Kj = 53.69 * 0.001

=> 0.05369 Kj

T = ΔH / ΔS

T = 49.09 / 0.05369

T = 914.32ºC

3 0

2 years ago

The half-life of radioactive substance is 2.5 minutes. what fraction of the origional radioactive remains after 10 mins

saul85 [17]

The answer is 1/16.

Half-life is the time required for the amount of a sample to half its value.
To calculate this, we will use the following formulas:
1. $(1/2)^{n} = x$ ,
where:
n - a number of half-lives
x - a remained fraction of a sample

2. $t_{1/2} = \frac{t}{n}$
where:
 $t_{1/2}$ - half-life
t - total time elapsed
n - a number of half-lives

So, we know:
t = 10 min
 $t_{1/2}$ = 2.5 min

We need:
n = ?
x = ?

We could first use the second equation to calculate n:
If:
$t_{1/2} = \frac{t}{n}$ ,
Then:
$n = \frac{t}{ t_{1/2} }$
⇒ $n = \frac{10 min}{2.5 min}$
⇒ $n=4$ 

Now we can use the first equation to calculate the remained fraction of the sample.
 $(1/2)^{n} = x$
⇒ $x=(1/2)^4$
⇒ $x= \frac{1}{16}$