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3 years ago

A physical change occur when a

Chemistry

2 answers:

Bess [88]3 years ago

6 0

Glue gun melts a glue stick would be the physical change.

Viefleur [7K]3 years ago

5 0

The answer is C. Glue gun melts a glue stick.

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The mole fraction of CO2 in a certain solution with H2O as the solvent is 3.6 × 10−4. What is the approximate molality of CO2 in

nataly862011 [7]

Answer: C) 0.020 m

Explanation:

Molality of a solution is defined as the number of moles of solute dissolved per kg of the solvent.

$Molality=\frac{n\times 1000}{W_s}$

where,

n = moles of solute

$W_s$ = weight of solvent in g

Mole fraction of $CO_2$ is = $3.6\times 10^{-4}$ i.e. $3.6\times 10^{-4}$ moles of $CO_2$ is present in 1 mole of solution.

Moles of solute $(CO_2)$ = $3.6\times 10^{-4}$

moles of solvent (water) = 1 - $3.6\times 10^{-4}$ = 0.99

weight of solvent = $moles\times {\text {Molar mass}}=0.99\times 18=17.82g$

Molality = $\frac{3.6\times 10^{-4}\times 1000}{17.82g}=0.020$

Thus approximate molality of $CO_2$ in this solution is 0.020 m

5 0

3 years ago

1. How is energy being used inefficiently?

ANTONII [103]

Answer:

1. Energy intensity (primary energy consumption divided by GDP) for the world and various countries. The lower the value, the less energy is used to generate economic output, so lower means more efficient in a sense.

2.Lower Your Thermostat. Adopt the habit of lowering the temperature on your thermostat while away from home.

Start a Compost Pile.

Install Low-Flow Showerheads.

Seal All Windows.

Limit Space Heater Use.

Turn Off Unnecessary Water.

Replace Incandescent Bulbs.

Unplug Unused Chargers.

5 0

1 year ago

Sometimes in lab we collect the gas formed by a chemical reaction over water (see sketch at right). This makes it easy to isolat

ad-work [718]

Answer:

The correct answer is 0.00582 grams.

Explanation:

In order to solve the question, let us consider the vapor pressure of H2O, as hydrogen gas is collected over water, therefore, we have to consider the vapor pressure of water in the given case. Let us assume that the pressure is 760 torr or 1 atm.

It is known that the vapor pressure of water at 40 degree C is 53.365 torr (Based on the data).

Therefore, the pressure of H2 will be,

P = 760-55.365 = 704.635 torr or 704.635/760 = 0.9272 atm

The volume of the hydrogen gas collected in the tube is 80 ml or 0.08 L

Temperature in Kelvin will be 40+273 = 313 K

To calculate the moles of hydrogen (H2) gas, there is a need to use the ideal gas equation, that is, PV= nRT, in this R is the gas constant, whose value is 0.0821 L atm/molK, and n is the moles of the gas.

By inserting the values in the equation we get:

PV = nRT

n = PV/RT = 0.9272 *0.08 / 0.0821 * 313

n = 0.00289 moles

The mass of H2 will be moles * molar mass = 0.00289 * 2.016

= 0.00582 grams.

7 0

3 years ago

Determine the total number of atoms contain in a 2.00 moles of Ni

spayn [35]

Answer:

2.00 moles of Ni has 1.2 *10^24 atoms

Explanation:

Step 1: Data given

Number of moles Ni = 2.00 moles

Number of Avogadro = 6.022*10^23 /mol

Step 2: Calculate number of atoms

Number of particles (=atoms) = Number of Avogadro * number of moles

Number of atoms = 6.022 * 10^23 /mol * 2.00 moles

Number of atoms = 1.2*10^24 atoms

2.00 moles of Ni has 1.2 *10^24 atoms

4 0

3 years ago

What do the individual spheres represent in the model!

Trava [24]

Answer:

the individual atom in the molecule

Explanation:

In chemistry, the ball-and-stick model is a molecular model of a chemical substance. Invidual spheres there represent atoms in the molecule. The bigger atomic number the atom has, the larger diameter of the spheres this atom has in this model.

I hope this answer will help you. Have a nice day !

5 0

2 years ago