How do you determine the volume of a regular object if you don't know the density?

How many grams of C5H12 must be burned to heat 1.39 kg of water from 21.2 °C to 97.0 °C? Assume that all the heat released durin

faust18 [17]

Answer:

m = 8.9856 g

Explanation:

In order to do this, we need to write the expressions that are to be used. First, to calculate heat:

Q = m*C*ΔT (1)

Where C would be heat capacity of the substance.

The heat can also be relationed with the moles and enthalpy of a compound using the following expression:

Q = n*ΔH (2)

Finally for the mass of any compound, we use the following expression:

m = n*MM (3)

So, in order to calculate the grams of pentane (C5H12), we need to calculate the moles of the compound, and to do that, we need the heat exerted.

So, as we are using water, let's calculate the heat that is been exerted with the water. The C of the water is 4.186 J/g °C so:

Q = (1.39 * 1000) * 4.186 * (21.2 - 97)

Q = -441,045.33 J

This is the heat neccesary to burn pentane and heat water. Now, with this value, let's calculate the moles used of pentane with expression (2). The ΔH of the pentane is -3,535 045.kJ/mol or -3.535x10⁶ J/mol. Solving for n we have:

n = -441,045.3 / -3.535x10⁶

n = 0.1248 moles

Finally, we can calculate the grams needed with expression (3). The molar mass of pentane is 72 g/mol

m = 0.1248 * 72

m = 8.9856 g

This is the mass needed to heat 1.39 kg of water

6 0

4 years ago

1.3625 of an unknown metal X reacts with oxygen to form 1.4158g of the oxide X2O what is the atomic mass of X?

FrozenT [24]

Answer:

The atomic mass of X is 204.5 amu.

Explanation:

We know that metals react with oxygen forming a metallic oxide, according to the following equation:

4 X + O₂ ⇄ 2 X₂O

The oxide is formed just by <em>just</em> two elements, the metal and oxygen. The total mass of the oxide is 1.4158g and the mass of the metal in the oxide must be 1.3625g because of the Law of conservation of mass. Then, we can substract the mass of the metal to obtain the mass of oxygen.

mass O + mass X = mass X₂O

mass O = mass X₂O - mass X = 1.4158g - 1.3625g = 0.0533g

So, for every 0.0533g of oxygen there are 1.3625 g of the metal X. In the formula X₂O there is 1 mol of atoms of oxygen, which has a molar mass of 16 g/mol. We can use this data to find out the mass of the metal in the oxide.

$16g(O).\frac{1.3625g(X)}{0.0533g(O)} =409g(X)$

Given in the formula there are 2 moles of atoms of X, the molar mass should be half of 409g, i.e., 204.5g/mol. If a mol of X has a mass of 204.5 g, an atom of X has a mass of 204.5 amu, according to its definition.

7 0

3 years ago

Define saturated and unsaturated fats

saul85 [17]

Answer:

SATURATED: Saturated fat is a type of fat in which the fatty acid chains have all or predominantly single bonds.

UNSATURATED: Unsaturated fats are loosely packed. They tend to be liquid at room temperature.

<em>There are two main types of unsaturated fat:</em>

<u>Monounsaturated</u>

<u>Polyunsaturated</u>

8 0

3 years ago

Question 1<br>How many atoms are there in 0.3 mol of<br>sodium? [L = 6.02 x 102 mot')

Aleksandr [31]

Answer:

<h2>1.806 × 10²³ atoms</h2>

Explanation:

The number of sodium atoms can be found by using the formula

where n is the number of moles

N is the number of entities

L is the Avogadro's constant which is

6.02 × 10²³ entities

From the question we have

N = 0.3 × 6.02 × 10²³

We have the final answer as

<h3>1.806 × 10²³ atoms</h3>

Hope this helps you

5 0

3 years ago

Polyatomic ion that is the conjugate acid of ammonia

mariarad [96]

Answer:

Ammonium,

N H + 4

Explanation:

Conjugate acid-base pairs consist of two compounds, differing by a charge of +/-1 due to the movement of a single proton

H

+

You use the bronstead description of acids and bases when calculating which is the conjugate acid and which is the conjugate base in a reaction. This theory explains that a bronstead acid is any molecule, ion or atom that can donate a proton and a bronstead base is any molecule, ion or atom that can accept a proton.

In this reaction, ammonia is the conjugate base and accepts a proton from water, where it becomes the conjugate acid ammonium. You can show that the lone pair of electrons on the nitrogen atom reacts with the hydrogen on water molecules, giving an ammonium ion and a hydroxide ion.

3 0

3 years ago