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3 years ago

14. Carbon-14 emits beta radiation and decays with a half-life (t) of 5730 years. Assume

Chemistry

1 answer:

Marizza181 [45]3 years ago

6 0

Answer: 375 g

Explanation:

Formula used :

$a=\frac{a_o}{2^n}$

where,

a = amount of reactant left after n-half lives = ?

$a_o$ = Initial amount of the reactant = 100 g

n = number of half lives = 4

Putting values in above equation, we get:

$a=\frac{6000}{2^4}$

$a=375g$

Therefore, the amount of carbon-14 remains at the end of four half-lives is 375 g

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What is the pH of a mixture of 0.042 M NaH2PO4 and 0.058 M Na2HPO4? Hint: The pKa of phosphate is 6.86.

AlekseyPX

Answer:

The pH value of the mixture will be 7.00

Explanation:

Mono and disodium hydrogen phosphate mixture act as a buffer to maintain pH value around 7. Henderson–Hasselbalch equation is used to determine the pH value of a buffer mixture, which is mathematically expressed as,

$pH=pK_{a} + log(\frac{[Base]}{[Acid]})$

According to the given conditions, the equation will become as follow

$pH=pK_{a} + log(\frac{[Na_{2}HPO_{4} ]}{[NaH_{2}PO_{4}]})$

The base and acid are assigned by observing the pKa values of both the compounds; smaller value means more acidic. NaH₂PO₄ has a pKa value of 6.86, while Na₂HPO₄ has a pKa value of 12.32 (not given, but it's a constant). Another more easy way is to the count the acidic hydrogen in the molecular formula; the compound with more acidic hydrogens will be assigned acidic and vice versa.

Placing all the given data we obtain,

$pH=6.86 + log(\frac{0.058}{0.042})$

$pH=7.00$

5 0

3 years ago

Please help due right now <br> 10 POINTS

Darya [45]

Answer:

F=ma

Explanation:

F=m×a

according to that F÷m=a and also F ÷a=m

3 0

3 years ago

When .080 moles of propane burn at STP, what volume of carbon dioxide is produced?

ahrayia [7]

Taking into account the reaction stoichiometry and the definition of STP, 5.4 L of carbon dioxide is produced.

<h3>Reaction stoichiometry</h3>

In first place, the balanced reaction is:

C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O

By reaction stoichiometry (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of moles of each compound participate in the reaction:

C₃H₈: 1 mole
O₂: 5 moles
CO₂: 3 moles
H₂O: 4 moles

<h3>Moles of CO₂ formed</h3>

The following rule of three can be applied: if by reaction stoichiometry 1 mole of C₃H₈ form 3 moles of CO₂, 0.080 moles of C₃H₈ form how many moles of CO₂?

$amount of moles of CO_{2} =\frac{0.080 moles of C_{3} H_{8}x3 moles of CO_{2} }{1 mole of C_{3} H_{8} }$

<u><em>amount of moles of CO₂= 0.24 moles</em></u>

<h3>Definition of STP condition</h3>

The STP conditions refer to the standard temperature and pressure. Pressure values at 1 atmosphere and temperature at 0 ° C are used and are reference values for gases. And in these conditions 1 mole of any gas occupies an approximate volume of 22.4 liters.

<h3>Volume of CO₂ produced</h3>

You can apply the following rule of three: If by definition of STP 1 mole of CO₂ occupies 22.4 L, 0.24 moles of CO₂ how much volume does it occupy?

$volume of CO_{2} =\frac{0.24 molesx22.4 L}{1 mole}$

<u><em>volume of CO₂= 5.376 L ≅ 5.4 L</em></u>

Finally, 5.4 L of carbon dioxide is produced.

Learn more about

the reaction stoichiometry:

<u>brainly.com/question/24741074</u>

<u>brainly.com/question/24653699</u>

STP conditions:

<u>brainly.com/question/26364483</u>

<u>brainly.com/question/8846039</u>

<u>brainly.com/question/1186356</u>

6 0

2 years ago

Which of the following are not single-displacement reactions?

Goshia [24]

Answer:

$\boxed{\text{B and C }}$

Explanation:

In a single-displacement reaction, one element exchanges partners with another element in a compound.

$\textbf{A. } \rm Fe + 2HCl \longrightarrow FeCl_2 + H_2$

This is a single-displacement reaction, because the element Fe exchanges partners with H in HCl.

$\textbf{B. } \rm KOH + HNO_3 \longrightarrow H_2O + KNO_3$

This is not a single-displacement reaction, because it is a reaction between two compounds.

This is a double displacement reaction in which the K⁺ and H⁺ cations change partners with the anions.

$\textbf{C. } \rm Na_2S + 2HCl \longrightarrow 2NaCl + H_2S$

This is not a single-displacement reaction. It is another double displacement reaction, in which the Na⁺ and H⁺ cations change partners with the anions.

$\textbf{D. } \rm Ca + 2HOH \longrightarrow Ca(OH)_2 + H_2$