How could you separate a mixture of rocks and sand

31 Which ion has the smallest radius? (1) O2-(2) S2-(3) Se2- (4) Te2-

bearhunter [10]

The answer 1) Oxygen. And another smallest radius is fluorine, because it is the first in the periodic table.

6 0

3 years ago

Carbon-14 (14C) dating assumes that the carbon dioxide on the Earth today has the same radioactive content as it did centuries a

Nataly [62]

Answer: The tree was burned 16846.4 years ago to make the ancient charcoal

Explanation:

The equation used to calculate rate constant from given half life for first order kinetics:

$t_{1/2}=\frac{0.693}{k}$

where,

$t_{1/2}$ = half life of the reaction = 5715 years

Putting values in above equation, we get:

$k=\frac{0.693}{5715yrs}=1.21\times 10^{-4}yrs^{-1}$

Rate law expression for first order kinetics is given by the equation:

$k=\frac{2.303}{t}\log\frac{[A_o]}{[A]}$

where,

k = rate constant = $1.21\times 10^{-4}yr^{-1}$

t = time taken for decay process = ? yr

$[A_o]$ = initial amount of the sample = 100 grams

[A] = amount left after decay process = 13 grams

Putting values in above equation, we get:

$1.21\times 10^{-4}=\frac{2.303}{t}\log\frac{100}{13}\\\\t=16864.4yrs$

Hence, the tree was burned 16846.4 years ago to make the ancient charcoal

8 0

2 years ago

7. What must you do before you make a hypothesis?

almond37 [142]

Answer:

Ask a question?

Explanation:

look at the scientific method uwu

6 0

3 years ago

How do you know that a sealed calorimeter is a closed system?

3241004551 [841]

Answer: Option (c) is the correct answer.

Explanation:

When a system is open then there will be exchange of energy between the system and surrounding.

Whereas when a system is closed then there will be no exchange of energy, that is, thermal energy will not flow into the atmosphere.

Thus, we can conclude that a sealed calorimeter is a closed system because thermal energy is not transferred to the environment.

5 0

3 years ago

Read 2 more answers

Calculate the change in pH when 71.0 mL of a 0.760 M solution of NaOH is added to 1.00 L of a solution that is 1.0O M in sodium

Eddi Din [679]

Explanation:

It is known that $pK_{a}$ value of acetic acid is 4.74. And, relation between pH and $pK_{a}$ is as follows.

pH = pK_{a} + log $\frac{[CH_{3}COOH]}{[CH_{3}COONa]}$

= 4.74 + log $\frac{1.00}{1.00}$

So, number of moles of NaOH = Volume × Molarity

= 71.0 ml × 0.760 M

= 0.05396 mol

Also, moles of $CH_{3}COOH$ = moles of $CH_{3}COONa$

= Molarity × Volume

= 1.00 M × 1.00 L

= 1.00 mol

Hence, addition of sodium acetate in NaOH will lead to the formation of acetic acid as follows.

$CH_{3}COONa + NaOH \rightarrow CH_{3}COOH$

Initial : 1.00 mol 1.00 mol

NaoH addition: 0.05396 mol

Equilibrium : (1 - 0.05396 mol) 0 (1.00 + 0.05396 mol)

= 0.94604 mol = 1.05396 mol

As, pH = pK_{a} + log $\frac{[CH_{3}COONa]}{[CH_{3}COOH]}$

= 4.74 + log $\frac{0.94604}{1.05396}$

= 4.69

Therefore, change in pH will be calculated as follows.

pH = 4.74 - 4.69

= 0.05

Thus, we can conclude that change in pH of the given solution is 0.05.

8 0

2 years ago