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3 years ago

How does air above a heated surface move?

1 answer:

6 0

When air is warmed up, its molecules move faster and faster and as a result they move further from each other. They still have the same mass, but they now occupy a larger volume. This means that its density is smaller.
The opposite when air is cooled off. The molecules slow down, get closer together, occupy a smaller volume and therefore its density is bigger.

When air is warmed up, it goes up. Once it's up there, is cools off and goes back down. Near the heated surface the air gets warmed up again, goes up, cools down, goes back down, and again and again.
that is called convection cells

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1. A substance, A₂B, has the composition by mass of 60% A and 40% B. What is the composition of AB₂ by mass?

Lubov Fominskaja [6]

This may help you
Use an arbitrary mass, 100 g is an easy number to work with. 60% of 100 g is 60 g, there are two A's. Each A is 30 g 40 g is B, and there is only one, so B is 40 g. AB2, would have a mass of 30 g + 2*40 g = 110 g The new percent by mass composition of A is: 30g110g∗100%=27.3% The new percent by mass composition of B is: 80g110g∗100%=72.7%

8 0

3 years ago

QUESTION 1 (POLL)

Airida [17]

Answer:

They stay the same

Explanation:

4 0

3 years ago

Using the balanced equation for the combustion of ethane: 2C2H6 + 7O2 → 4CO2 + 6H2O, how many moles of O2 needed to produce 12 m

pickupchik [31]

Answer:

14 moles of oxygen needed to produce 12 moles of H2O.

Explanation:

We are given that balance eqaution

$2C_2H_6+7O_2\rightarrow 4CO_2+6H_2O$

We have to find number of moles of O2 needed to produce 12 moles of H2O.

From given equation

We can see that

6 moles of H2O produced by Oxygen =7 moles

1 mole of H2O produced by Oxygen= $\frac{7}{6}$ moles

12 moles of H2O produced by Oxygen= $\frac{7}{6}\times 12$ moles

12 moles of H2O produced by Oxygen= $7\times 2$ moles

12 moles of H2O produced by Oxygen=14 moles

Hence, 14 moles of oxygen needed to produce 12 moles of H2O.

3 0

2 years ago

To interconvert the concentration units molality (m) and mass percent, you must also know the density of the solution. A) True B

uranmaximum [27]

Answer:

The correct answer is option false.

Explanation:

Molality of the solution defined as moles of substance present in 1 kilogram of solvent.

Moles = $\frac{Mass of solute}}{\text{molar mass of solute}}$

$Molality=\frac{Moles}{\text{Mass of solvent(kg)}}$

Mass of percent (w/w%) of the solution is defined as amount of solute present in 100 grams of solution.

$(w/w\%)_=\frac{\text{Mass of solute}}{\text{Mass of solution}}\times 100$

So, if want to inter-convert molality into mass percent we can do that without knowing density of solution.

Mass of solution = Mass of solute + Mass of solvent

7 0

3 years ago

Which of the following statements concerning a metal crystallized in a face-centered cubic cell is/are CORRECT? 1. One metal ato

AleksAgata [21]

Answer:

Only 3 is correct.

Explanation:

The crystal of a metal or an ionic compound is called a cell, and there are 7 types of unit cells: cubic, tetragonal, orthorhombic, monoclinic, hexagonal, rhombohedral, and triclinic.

In a face-centered cubic cell (FCC) all angles are 90º and all lengths are equal. Each cubic cell has 8 atoms in each corner of the cube, and that atom is shared with 8 neighboring cells. So for a metal crystal, the atom is located at each of the eight lattice points, where it is shared equally between eight unit cells.

5 0

3 years ago