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bagirrra123 [75]
3 years ago
8

The density of iron is 7.8 g/cm3 and that of aluminum is 2.7 g/cm3. Using a balance, you find that a block of iron has the same

mass as a block of aluminum. Which block has the LARGER volume?
Question 15 options:

You cannot tell from the information given.


The volumes are the same.


The iron block


The aluminum block
2.) As water in an ice cube tray freezes,

Question 23 options:

it absorbs energy from its surroundings.


its surroundings absorb energy from it.


it absorbs coldness from and releases energy to its surroundings.


it only absorbs the coldness from its surroundings.


it neither absorbs nor releases energy, because its temperature stays constant.
Chemistry
1 answer:
vazorg [7]3 years ago
8 0

Answer:

1.The Aluminum block

2.its surroundings absorb energy from it.

Explanation:

In this question it is important to remember that density of an object is the mass of that object divided by its volume.

The expression applied here is density=mass/volume

Given that the mass is constant,lets say mass= m=1g

and density of aluminum=2.7g/cm³ and that of iron is 7.8 g/cm³ then volume=?

Volume=mass/density

Volume of aluminum= 1/2.7 =0.3704 cm³

Volume of iron = 1/7.8 =0.1282 cm³

Here we see volume of Aluminum block is the largest.

2.As water in an ice cube tray freezes, its surroundings absorb energy from it.When the water freezes, latent heat of freezing is given out to the surrounding.When water is freezing, it stays at a constant temperature of 0°C, the heat energy released ensures that there is no cooling past 0 °C.

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Determine the empirical and molecular formula for chrysotile asbestos. Chrysotile has the following percent composition: 28.03%
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<u>Answer:</u> The empirical and molecular formula of chrysotile is Mg_3Si_2H_3O_4 and Mg_6Si_4H_6O_{16}

<u>Explanation:</u>

We are given:

Percentage of Mg = 28.03 %

Percentage of Si = 21.60 %

Percentage of H = 1.16 %

Percentage of O = 49.21 %

Let the mass of compound be 100 g. So, percentages given are taken as mass.

Mass of Mg = 28.03 g

Mass of Si = 21.60 g

Mass of H = 1.16 g

Mass of O = 49.21 g

To formulate the empirical formula, we need to follow some steps:

  • <u>Step 1:</u> Converting the given masses into moles.

Moles of Magnesium = \frac{\text{Given mass of Magnesium}}{\text{Molar mass of Magnesium}}=\frac{28.03g}{24g/mole}=1.17moles

Moles of Silicon = \frac{\text{Given mass of Silicon}}{\text{Molar mass of Silicon}}=\frac{21.06g}{28g/mole}=0.752moles

Moles of Hydrogen = \frac{\text{Given mass of Hydrogen}}{\text{Molar mass of Hydrogen}}=\frac{1.16g}{1g/mole}=1.16moles

Moles of Oxygen = \frac{\text{Given mass of oxygen}}{\text{Molar mass of oxygen}}=\frac{49.21g}{16g/mole}=3.07moles

  • <u>Step 2:</u> Calculating the mole ratio of the given elements.

For the mole ratio, we divide each value of the moles by the smallest number of moles calculated which is 0.752 moles.

For Magnesium = \frac{1.17}{0.752}=1.5

For Silicon = \frac{0.752}{0.752}=1

For Hydrogen = \frac{1.16}{0.752}=1.5

For Oxygen = \frac{3.07}{0.485}=4.08\approx 4

To convert the mole ratios into whole numbers, we multiply individual mole ratios by 2

Mole ratio of Magnesium = (2 × 1.5) = 3

Mole ratio of Silicon = (2 × 1) = 2

Mole ratio of Hydrogen = (2 × 1.5) = 3

Mole ratio of Oxygen = (2 × 4) = 8

  • <u>Step 3:</u> Taking the mole ratio as their subscripts.

The ratio of Mg : Si : H : O = 3 : 2 : 3 : 8

The empirical formula for the given compound is Mg_3Si_2H_3O_8

For determining the molecular formula, we need to determine the valency which is multiplied by each element to get the molecular formula.

The equation used to calculate the valency is :

n=\frac{\text{Molecular mass}}{\text{Empirical mass}}

We are given:

Mass of molecular formula = 520.8 g/mol

Mass of empirical formula = [(24 × 3) + (28 × 2) + (1 × 3) + (16 × 8)] = 259 g/mol

Putting values in above equation, we get:

n=\frac{520.8g/mol}{259g/mol}=2

Multiplying this valency by the subscript of every element of empirical formula, we get:

Mg_{(3\times 2)}Si_{(2\times 2)}H_{(3\times 2)}O_{(8\times 2)}=Mg_6Si_4H_6O_{16}

Hence, the empirical and molecular formula of chrysotile is Mg_3Si_2H_3O_4 and Mg_6Si_4H_6O_{16}

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