Which of the following are base formulas? (Choose 2)

A 2.50 g sample of zinc is heated, then placed in a calorimeter containing 65.0 g of water. Temperature of water increases from

USPshnik [31]

Answer:

719.83°C

Explanation:

The heat that the sample of Zinc gives is equal to the heat that water is absorbing. That is:

C(Zn) * m(Zn) * ΔT(Zn) = C(H2O) * m(H2O) * ΔT(H2O)

Where:

C is specific heat (Zn: 0.390J/g°C; H2O: 4.184J/g°C)

m is mass (Zn: 2.50g; H2O: 65.0g)

ΔT (Zn: ?; H2O: (22.5°C - 20.0°C = 2.50°C)

Replacing:

0.390J/g°C * 2.50g * ΔT(Zn) = 4.184J/g°C * 65.0g * 2.50

ΔT(Zn) = 697.33°C

As final temperature of Zn is 22.50°C, initial temperature is:

Initial temperature: 697.33°C + 22.50°C

719.83°C

3 0

3 years ago

Gold is alloyed with other metals to increase its hardness in making jewelery.a) Consider a piece of gold jewelry the weighs 9.8

irinina [24]

Answer:

A). Percentage of gold by mass of the jewellery =

(6.059÷9.85) × 100 = 61.5%

B). Purity of the gold = 0.615 × 24 = 14.76 karat ~ 15 karat gold

Explanation:

Mass of jewellery = 9.85g Volume of jewellery = 0.675cm^3.

Density of gold = 19.3g/cm^3 and density of silver = 10.5g/cm^3

Let the volume of gold in the jewellery be X and the volume of silver in the jewellery be Y

Hence we have

Density = mass/volume or mass = volume × density = for gold = X × 19.3g/cm^3 and for the silver = Y × 10.5g/cm^3

19.3X +10.5Y = 9.85g

Also volume of jewellery is given by

Volume of silver in the jewellery + volume of gold in the jewellery = 0.675cm^3.

X + Y = 0.675cm^3.

Solving the above equations we have

Y = 0.675 - X

Which gives

19.3X + 10.5Y = 9.85g

19.3X + 10.5 × (0.675 - X) =9.85g

19.3X + 7.0875 - 10.5X = 9.85

8.8X + 7.0875 = 9.85

8.8X = 2.7625

or X = 0.3139 cm^3

But Y = 0.675 - X

Hence Y = 0.675 - 0.3139 = 0.3611 cm^3

Mass of gold in the jewellery = volume of gold × Density of gold = 0.3139 × 19.3 = 6.059 g

Also mass of silver = 10.5 × 0.3611 = 3.7913g

A). Percentage of gold by mass of the jewellery =

(6.059÷9.85) × 100 = 61.5%

B). Purity of the gold = 0.615 × 24 = 14.76 karat ~ 15 karat gold

7 0

3 years ago

When the temperature of a gas in a rigid container decreases, the particles of the gas move slower and experience fewer collisio

4vir4ik [10]

When the temperature of a gas within a rigid container decreases, the particles on average move more slowly and do not collide with one another or the container walls as often. It is the the ideal gas law that applies in this situation and states that a decrease in the temperature of a gas also results in a decrease in the pressure. Thus, automobile tyres which have a colder gas in the winter sometimes need additional air to provide suffiicient pressure.

6 0

3 years ago

Read 2 more answers

What is the molarity of a sodium chloride solution made by dissolving 4.512 moles to make 2.0 L?

Svet_ta [14]

Answer:

2.40 M

Explanation:

The molarity of a solution tells you how many moles of solute you get per liter of solution.

Notice that the problem provides you with the volume of the solution expressed in milliliters,

mL

. Right from the start, you should remember that you must convert this volume to liters by using the conversion factor

1 L

=

10

3

mL

Now, in order to get the number of moles of solute, you must use its molar mass. Now, molar masses are listed in grams per mol,

g mol

−

1

, which means that you're going to have to convert the mass of the sample from milligrams to grams

1 g

=

10

3

mg

Sodium chloride,

NaCl

, has a molar mass of

58.44 g mol

−

1

, which means that your sample will contain

unit conversion



280.0

mg

⋅

1

g

10

3

mg

⋅

molar mass



1 mole NaCl

58.44

g

=

0.004791 moles NaCl

This means that the molarity of the solution will be

c

=

n

solute

V

solution

c

=

0.004791 moles

2.00

⋅

10

−

3

L

=

2.40 M

The answer is rounded to three sig figs, the number of sig figs you have for the volume of the solution.

6 0

3 years ago

What form of energy causes an ice cube to melt

zalisa [80]

Answer:

Thermal

Explanation:

When something heats up its atoms become further apart making it melt when something heats up or gets heat or loses heat that's thermal energy

6 0

3 years ago