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ahrayia [7]
3 years ago
13

If the half-life of a radioactive substances is 590 million years and you have 40 atoms of it, how many half-lives will have pas

sed when 5 atoms remain
Chemistry
1 answer:
Nady [450]3 years ago
3 0

Answer:

3

Explanation:

Applying,

2^{n'} = R/R'............... Equation 1

Where n' = number of halflives that have passed, R = Original atom of the substance, R' = atom of the substance left after decay.

From the question,

Given: R = 40 atoms, R' = 5 atoms

Substitute these values into equation 1

2^{n'} = 40/5

2^{n'} = 8

2^{n'} = 2³

Equation the base,

n' = 3

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<img src="https://tex.z-dn.net/?f=H_2PO_4%5E-%28aq%29%20%5Crightarrow%20H%5E%2B%28aq%29%20%2B%20HPO_4%5E%7B2-%7D%28aq%29" id="Te
klasskru [66]

Answer:

The pH of the buffer solution = 8.05

Explanation:

Using the Henderson - Hasselbalch equation;

pH = pKa₂ + log ( [HPO₄²-]/[H₂PO4⁻]

where pKa₂ = -log (Ka₂) = -log ( 6.1 * 10⁻⁸) = 7.21

Concentration of OH⁻ added = 0.069 M (i.e. 0.069 mol/L)

[H₂PO4⁻] after addition of OH⁻ = 0.165 - 0.069 = 0.096 M

[HPO₄²-] after addition of OH⁻ = 0.594 + 0.069 = 0.663 M

Therefore,

pH = 7.21 + log (0.663 / 0.096)

pH = 7.21 + 0.84

pH = 8.05

4 0
3 years ago
A solid precipitates from a solution, absorbing heat as it does so. a. Yes b. No c. Can't decide with information given.
inn [45]

Answer:

c. Can't decide with information given.

Explanation:

The chemical and physical processes can be classified as endothermic or exothermic. The first one happens when the system absorbs heat, so the temperature of the surroundings will decrease, and the other one happens when the system releases heat, then the temperature of the surrounds will increase.

Precipitation is the formation of a solid in a solution. The process can happen with absorption or release of heat, it depends on the substance. So, with the information given it's impossible to say it.

3 0
3 years ago
Calculate the mass of Na2O that can be produced by the chemical reaction of 4.0 grams of sodium with excess oxygen in the reacti
e-lub [12.9K]

Answer:

The mass of Na₂O that can be produced by the chemical reaction of 4.0 grams of sodium with excess oxygen in the reaction is 5.39 grams.

Explanation:

You know  the balanced reaction:

4 NA + O₂ ⟶ 2 Na₂O

By stoichiometry of the reaction (that is, the relationship between the amount of reagents and products in a chemical reaction) react and are produced:

  • Na: 4 moles
  • O₂: 1 mole
  • Na₂O: 2 moles

Being:

  • Na: 23 g/ole
  • O: 16 g/mole

the molar mass of the compounds participating in the reaction is:

  • Na: 23 g/mole
  • O₂: 2*16 g/mole= 32 g/mole
  • Na₂O: 2*23 g/mole +16 g/mole=  62 g/mole

Then by stoichiometry of the reaction they react and are produced:

  • Na: 4 moles* 23 g/mole= 92 g
  • O₂: 1 mole*32  g/mole= 32 g
  • Na₂O: 2 moles* 62 g/mole= 124 g

Then you can apply the following rule of three: if 92 grams of Na produce 124 grams of Na₂O, 4 grams of Na, how much mass of Na₂O does it produce?

massofNa_{2}O =\frac{4 grams of Na*124 gramsofNa_{2}O }{92 grams of Na}

mass of Na₂O=5.39 g

<em><u>The mass of Na₂O that can be produced by the chemical reaction of 4.0 grams of sodium with excess oxygen in the reaction is 5.39 grams.</u></em>

8 0
3 years ago
How many atoms does C₆H₄Cl₂ have?
Charra [1.4K]

Answer:

There are 12 atoms in the compound

6 0
3 years ago
Compare the structure and function of rhizoids and stolons? please help I need this answer for science
ladessa [460]
structural difference between  Rhizoids and  stolons
 Rhizoids   are  root  like  structure  organs    while   stolons  are a  specialized  type  of  horizontal   above  the  ground

functional  difference
 Rhizoids  absorb  water  and  nutrient ,  They  keep  plant  attached  on  the  soil  while  stolons  are  propagation  of  the  plant.
7 0
3 years ago
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