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Eddi Din [679]
3 years ago
7

A student submits the following work on the mass number, but he has made a few mistakes. Select all of his mistakes.

Chemistry
2 answers:
MatroZZZ [7]3 years ago
8 0

Answer:

1. <u>Calculating the mass number for an atom requires that we know the atomic number and the number of protons in the atom's nucleus.</u>

2. <u>The mass number then gives us the average weight of atoms of a given element.</u>

3. <u>However, as long as the number of protons equals the number of neutrons, the values balance out and we always obtain a whole number for the mass number.</u>

Explanation:

MatroZZZ [7]3 years ago
4 0

Do you know the answer?

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I need this very fast so please answer this first! I will mark you as the Brainiest and put my max points so please hurry!!!
Korolek [52]

Answer:

Answer C

Explanation:

Heat is used to turn the solid ice into liquid water

3 0
3 years ago
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During ______ the composition of a substance does not change
nignag [31]
During the Physical changes
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3 years ago
Calculate the % composition of the unknown liquid using your most precise result. It is a mixture of ethanol (D[ETOH] = 0.7890 g
Rufina [12.5K]

% composition of ethanol = 34.51%

% composition of water  = 65.49%

<h3>What is density?</h3>

A material's density is defined as its mass per unit volume.

Given data:

The density of ethanol = 0.7890 g/mL

The density of water = 0.9982 g/mL

The density of mixture = 0.926 g/mL

Let the % composition of ethanol = x

Let the % composition of water = 100-x

Now density of the mixture

\frac{Mass}{Volume}

Mass = \frac{percent  \;of  \;ethanol  \;X  \;density  \;of  \;ethanol  \;+  \\ \;percent  \;of  \;water X  \;density  \;of  \;water}{100}

0.926 = \frac{x X  0.7890 g/mL  \;+  (100-x) X  0.9982 g/mL}{100}

x= 34.51 %

Hence,

% composition of ethanol = 34.51%

% composition of water = 65.49%

Learn more about the density here:

brainly.com/question/952755

#SPJ1

8 0
2 years ago
A) Compute the repeat unit molecular weight of polystyrene. B) Compute the number-average molecular weight for a polystyrene for
Andrej [43]

Answer:

Explanation:

In Polystrene, the molecular formula for the repeat unit = C_8H_8;

and the atomic weights of Carbon C = 12.01 g/mol

For Hydrogen, it is 1.01 g/mol

Hence, the repeat unit molecular weight is:

m = 8 (12.01 g/mol)+8(1.01 g/mol)

m = 96.08 g/mol + 8.08 g/mol

m = 104.16 g/mol

The degree of polymerization = no-average molecular weight/repeat unit molecular weight.

Mathematically;

DP = \dfrac{\overline M_n}{m}

\overline M_n= DP \times m

\overline M_n= 25000 \times 104.16 \ g/mol

\overline M_n= 2604000  \ g/mol

7 0
3 years ago
What does the release or absorption of energy indicate
Illusion [34]
Chemical change
Hope this helps!
4 0
3 years ago
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