Convert 1.5 km to millimeters, and express the result in scientific notation.

A thin sheet of aluminum can block _____.

BartSMP [9]

It can block light. Please mark Brainliest!!!

6 0

3 years ago

PLZ HELP ...The half-life of polonium-218 is 3.0 minutes. If you start with 40.0 g, how long will it be before only 4.5 g remain

Elanso [62]

Answer:- 9.4 minutes.

Solution:- Radioactive decay obeys first order reaction kinetics and the equation used to solve this type of problems is:

$lnN=-kt+lnN_0$

where, k is decay constant and t is the time. $N_0$ is the initial amount of the radioactive substance and N is the remaining amount.

Since the value of decay constant is not given, so we need to calculate it first from given half life by using the formula:

$k=\frac{0.693}{t_1_/_2}$

where $t_1_/_2$ stands for half life.

Given half life is 3.0 minutes.

So, $k=\frac{0.693}{3.0min}$

$k=0.231min^-^1$

Let's plug in the values in the first order reaction equation and solve it for t.

$ln4.5g=-0.231min^-^1(t)+ln40.0g$

It could also be written as:

$ln(\frac{4.5g}{40.0g})=-0.231min^-^1}$

$-2.18=-0.231min^-^1}$

$t=\frac{-2.18}{-0.231min^-^1}$

k = 9.4 min

So, the radioactive substance would take 9.4 minutes to decay from 40.0 grams to 4.5 grams.

4 0

3 years ago

Enter your answer in the provided box. calculate the ph of a 0. 39 m ch3cooli solution. (ka for acetic acid = 1. 8 × 10−5. )

loris [4]

The pH of the solution is the negative logarithm of a proton or the hydrogen ion concentration. The pH of 0.39 M acetic acid solution (CH₃COONa) is 2.58.

The pH has been said to be the hydrogen ion concentration that can also be given by the pOH.

Given,

The acid dissociation constant Ka = 1.8 × 10⁻⁵

Concentration of acetic acid (C) = 0.39 M

The hydrogen ion concentration from Ka and molar concentration are calculated as:

H⁺ = √ Ka × C

= √1.8 × 10⁻⁵ × 0.39

= √0.00000702

= 0.0026

Now, pH from hydrogen ion is calculated as,

pH = - log [H⁺]

= - log [0.0026]

= 2.58

Therefore, the pH of acetic acid is 2.58.

Learn more about pH here:

brainly.com/question/27549063

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6 0

2 years ago

Which of the following are producers?

nikklg [1K]

All of the above is the answer

7 0

3 years ago

Read 2 more answers

Structure of 2,3-dimethylheptane

olga55 [171]

Answer:

Please find the structure of the hydrocarbon in the attachment section and details on how to draw it in the explanation section.

Explanation:

Heptane is a member of the alkane group, which has a general formula of CnH2n+2. If n in heptane is 7, this means that the chemical formula for heptane will be C7H16 i.e.

= C7H2(7) + 2

= C7H14+2

= C7H16

C7H16 is the chemical formula for heptane, which is a linear hydrocarbon with 7 carbon atoms and 16 hydrogen atoms. However, in the name of the hydrocarbon compound given in the question: 2,3-dimethylheptane;

- Two methyl groups (CH3) has a substituted two hydrogen atoms specifically at carbon 2 and 3 respectively. Therefore, the new chemical formula of 2,3-dimethylheptane will be: C7H14(CH3)2

Please find the structural formula of the compound; 2,3-dimethylheptane as an attachment.

3 0

3 years ago