Ask question

Ask question

All categories

3 years ago

14

Caffeine, a stimulant found in coffee and soda, has the following elemental composition: 49.48% carbon, 5.19% hydrogen, 16.48% o

xygen and 28.85% nitrogen. The molar mass of caffeine is 119.19 g/mol. Determine the molecular formula of caffeine.

1 answer:

prisoha [69]3 years ago

3 0

Answer:

Explanation:

C = 49.48

H = 5.19

O = 16.48

N = 28.85

ratio of moles

= 49.48 / 12 : 5.19 / 1 : 16.48 / 16 : 28.85 / 14

= 4.123 : 5.19 : 1.03 : 2.06

= 4 : 5 : 1 : 2

so the empirical formula = C₄ H₅O N₂

Let molecular formula = ( C₄ H₅ON₂ )ₙ ,

n ( 48 + 5 + 16 + 28 ) = 119.19

97 n = 194.19

n = 2 ( approx )

molecular formula = C₈ H₁₀O₂ N₄

You might be interested in

Select the correct answer from each drop-down menu.

postnew [5]

Answer:

Among the different types of scientific knowledge hypotheses are likely to be modified or discarded most frequently. Long ago in the 1600's scientists discarded the phlogiston theory because the new evidence didnt support it.

Explanation:

Hypothesis is the assumption of something possible or impossible to draw a consequence and is provisionally established as the basis for an investigation and which can confirm or deny its validity. For this reason, within scientific research, hypotheses are so important and so changeable that they are modified or discarded more frequently within scientific knowledge.

Based on a work by Johann Joachim Becher, the German scientist Georg Ernst Stahl created the phlogiston theory that said combustion occurred with certain materials because they had an “element” or a common flammable principle that was released at the time of burning . This theory was abandoned because there was no evidence, even through scientific experiments, to prove that this theory is true.

8 0

3 years ago

Calculate the number of water (H2O) molecules produced from the decomposition of 75.50 grams of Iron (III) hydroxide (Fe(OH)3).

Phantasy [73]

Answer: $6.38\times 10^{23}$ molecules of water are produced.

Explanation:

To calculate the moles :

$\text{Moles of solute}=\frac{\text{given mass}}{\text{Molar Mass}}$

$\text{Moles of} Fe(OH)_3=\frac{75.50g}{106.8g/mol}=0.707moles$

The balanced chemical reaction is:

$2Fe(OH)_3\rightarrow Fe_2O_3+3H_2O$

According to stoichiometry :

2 moles of $Fe_2O_3$ produce = 3 moles of $H_2O$

Thus 0.707 moles of $Fe_2O_3$ will produce= $\frac{3}{2}\times 0.707=1.06moles$ of $H_2O$

According to avogadro's law, 1 mole of every substance contains avogadro's number $6.023\times 10^{23}$ of particles.

Thus 1.06 moles of $H_2O$ contains = $\frac{6.023\times 10^{23}}{1}\times 1.06=6.38\times 10^{23}$ molecules

5 0

3 years ago

For the reaction H2PO4- HAsO4 2-HPO4 2-+H2AsO4- <br> what species are a conjugate acid-base pair?

aleksklad [387]

Ionic equation:

$\text{H}_2\text{PO}_4^{-} + \text{HAsO}_4^{2-} \to \text{HPO}_4^{2-} + \text{H}_2\text{AsO}_4^{-}$

The acid and base in a conjugate pair differ by only one proton $\text{H}^{+}$ . The acid loses one proton to produce a conjugate base, whereas the base gains a proton to produce its conjugate acid.

$\text{H}_2\text{PO}_4^{-}$ loses one proton to produce $\text{HPO}_4^{2-}$ in this reaction.

$\text{H}_2\text{PO}_4^{-} \to \text{H}^{+} + \text{HPO}_4^{2-}$

Meanwhile, $\text{HAsO}_4^{2-}$ gains one proton to form $\text{H}_2\text{AsO}_4^{-}$ .

$\text{HAsO}_4^{2-} + \text{H}^{+} \to \text{H}_2\text{AsO}_4^{-}$

Therefore

$\text{H}_2\text{PO}_4^{-}$ is the conjugate acid $\text{HPO}_4^{2-}$ , its conjugate base.
$\text{HAsO}_4^{2-}$ is the conjugate base of $\text{H}_2\text{AsO}_4^{-}$ , its conjugate acid.

8 0

3 years ago

Read 2 more answers

What volume (in liters) of a solution contains 0.14 mol of KCl?

oksano4ka [1.4K]

Answer:

$\boxed {\boxed {\sf 0.078 \ L }}$

Explanation:

We are asked to find the volume of a solution given the moles of solute and molarity.

Molarity is a measure of concentration in moles per liter. It is calculated using the following formula:

$molarity= \frac{moles \ of \ solute}{liters \ of \ solution}$

We know there are 0.14 moles of potassium chloride (KCl), which is the solute. The molarity of the solution is 1.8 molar or 1.8 moles of potassium chloride per liter.

moles of solute = 0.14 mol KCl
molarity= 1.8 mol KCl/ L
liters of solution=x

Substitute these values/variables into the formula.

$1.8 \ mol \ KCl/ L = \frac { 0.14 \ mol \ KCl}{x}$

We are solving for x, so we must isolate the variable. First, cross multiply. Multiply the first numerator and second denominator, then the first denominator and second numerator.

$\frac {1.8 \ mol \ KCl/L}{1} = \frac{0.14 \ mol \ KCl}{x}$

$1.8 \ mol \ KCl/ L *x = 1*0.14 \ mol \ KCl$

$1.8 \ mol \ KCl/ L *x = 0.14 \ mol \ KCl$

Now x is being multiplied by 1.8 moles of potassium chloride per liter. The inverse operation of multiplication is division, so we divide both sides by 1.8 mol KCl/L.

$\frac {1.8 \ mol \ KCl/ L *x}{1.8 \ mol \ KCl/L} = \frac{0.14 \ mol \ KCl}{1.8 \ mol \ KCl/L}$

$x= \frac{0.14 \ mol \ KCl}{1.8 \ mol \ KCl/L}$

The units of moles of potassium chloride cancel.

$x= \frac{0.14 }{1.8 L}$

$x=0.07777777778 \ L$

The original measurements of moles and molarity have 2 significant figures, so our answer must have the same. For the number we found, that is the thousandth place. The 7 in the ten-thousandth place tells us to round the 7 up to a 8.

$x \approx 0.078 \ L$

There are approximately <u>0.078 liters of solution.</u>

5 0

3 years ago

How much heat is absorbed when 447 g of water , Cp = 4.184 J/goC, goes from 25.0 oC to 35.0 oC?

Digiron [165]

Answer:

The answer to your question is Q = 18702.5 J

Explanation:

Data

mass of water = m = 447 g

Cp = 4.184 J/g°C

Temperature 1 = T1 = 25°C

Temperature 2 = T2 = 35°C

Heat = Q = ? Joules

Process

1.- Write the formula to calculate heat

Q = mCp(T2 - T1)

2.- Substitution

Q = (447)(4.184)(35 - 25)

3.- Simplification

Q = (447)(4.184)(10)

4.- Result

Q = 18702.5 J

8 0

3 years ago