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3 years ago

PLEASE HELP!!

Chemistry

2 answers:

AleksandrR [38]3 years ago

7 0

It's letter D.) 235/92 U + 4/2 He = 239/94 PU

maks197457 [2]3 years ago

5 0

Answer: D) $_{94}^{239}\textrm{Pu}$

Explanation:

Alpha decay : When a larger nuclei decays into smaller nuclei by releasing alpha particle. In this process, the mass number and atomic number is reduced by 4 and 2 units respectively.

General representation of alpha decay :

$_Z^A\textrm{X}\rightarrow _{Z-2}^{A-4}Y+_2^4{He}$

Thus $_{94}^{239}\textrm{Pu}\rightarrow _{94-2}^{239-4}Y+_2^4{He}$

$_{94}^{239}\textrm{Pu}\rightarrow _{92}^{235}U+_2^4{He}$

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HELP ME please i need help with this

nadezda [96]

4)
a) Natural selection will work negatively against rabbits that only eat berries as the drought is preventing berries from growing. It wont have any negative impact on rabbits that only eat grass as the grass is still surviving.

b) The statement ‘population has variations’ is backed up by the fact that the rabbits eat different things. They aren’t all the same. The statement ‘some variations are favorable’ is backed up by the fact that the rabbits that only eat grass are able to survive the drought. Their variation in eating grass instead of berries let’s them live. The statement ‘a population will change over time’ is backed up by the fact that the rabbits that only eat berries will die out. This will not only change the size of the population but going forward will create a population that has more rabbits that eat only grass on account of natural selection.

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3 years ago

What is the percent by mass of hydrogen in aspirin (c9h8o4)?

d1i1m1o1n [39]

Calculate the Mr of aspirin, next workout the percentage of H/aspirin

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3 years ago

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1. Consider the unbalanced equation:

Andrei [34K]

Answer:

1.) 17.76 moles H₂O

2.) 323.1 g HCN

Explanation:

1.) An equation is balanced when there is an equal amount of each element on both sides of the reaction. The quantities can be modified by adding coefficients in front of the molecules.

The unbalanced equation:

Al₄C₃(s) + H₂O -----> Al(OH)₃(s) + CH₄(g)

Reactants: 4 aluminum, 3 carbon, 2 hydrogen, 1 oxygen

Products: 1 aluminum, 1 carbon, 7 hydrogen, 3 oxygen

The balanced equation:

Al₄C₃(s) + 12 H₂O -----> 4 Al(OH)₃(s) + 3 CH₄(g)

Reactants: 4 aluminum, 3 carbon, 24 hydrogen, 12 oxygen

Products: 4 aluminum, 3 carbon, 24 hydrogen, 12 oxygen

Now that the equation is balanced, you can use the relevant coefficients to construct a mole-to-mole ratio. This will allow you to convert between moles Al₄C₃ to moles H₂O.

1.48 moles Al₄C₃ 12 moles H₂O
---------------------------- x ------------------------ = 17.76 moles H₂O
1 mole Al₄C₃

2.) To find the mass of HCN, you need to (1) convert grams NH₃ to moles NH₃ (via molar mass), then (2) convert moles NH₃ to moles HCN (via mole-to-mole from equation coefficients), and then (3) convert moles HCN to grams HCN (via molar mass). It is important to arrange the coefficients in a way that allows for the cancellation of units.

Molar Mass (NH₃): 14.009 g/mol + 3(1.008 g/mol)

Molar Mass (NH₃): 17.033 g/mol

Molar Mass (HCN): 1.008 g/mol + 12.011 g/mol + 14.009 g/mol

Molar Mass (HCN): 27.028 g/mol

2 CH₄(g) + 3 O₂(g) + 2 NH₃(g) ------> 2 HCN(g) + 6 H₂O(g)

203.6 g NH₃ 1 mole 2 moles HCN 27.028 g
--------------------- x ---------------- x ------------------------ x ----------------- =
17.033 g 2 moles NH₃ 1 mole

= 323.1 g HCN

8 0

2 years ago

Explain how to choose a proper indicator in an acid-base titration such as adding a strong acid (HCI) to a strong base (NaOH) ,

Jet001 [13]

The pH of the solution at equivalence point is dependent on the strength of the acid and strength of the base used in the titration.

For strong acid-strong base titration, pH = 7 at equivalence point
For weak acid-strong base titration, pH > 7 at equivalence point
For strong acid-weak base titration, pH < 7 at equivalence point

https://www.khanacademy.org/test-prep/mcat/chemical-processes/titrations-and-solubility-equilibria/a...

The indicator changes color when the pH changes at the endpoint of the titration. So, you need to determine what is present at the point and find the pH at the point. Then, you can reference a table of indicators to choose one whose color will change over the pH that includes your equivalency point.

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3 years ago

V=nT/P

lyudmila [28]

I believe the correct answer is the third option. It is the Avogadro's Law that should be used to determine the relationship between the volume and the number of moles in the equation. This law relates the volume and the the amount in moles of a gas.

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PLEASE HELP!!