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2 years ago

How much energy is transferred when 30.0 g of water is cooled from 25.0 °C to 12.7 °C.

Chemistry

1 answer:

enot [183]2 years ago

6 0

Answer:

Heat transferred, Q = 1542.42 J

Explanation:

Given that,

Mass of water, m = 30 grams

Initial temperature, $T_i=25^{\circ} C$

Final temperature, $T_f=12.7^{\circ} C$

We need to find the energy transferred. The energy transferred is given by :

$Q=mc\Delta T$

c is specific heat of water, c = 4.18 J/g °C

So,

$Q=30\ g\times 4.18\ J/g-^{\circ} C\times (12.7-25)\ ^{\circ} C\\\\Q=-1542.42\ J$

So, 1542.42 J of energy is transferred.

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A gas is contained in a thick-walled balloon. When the pressure changes from 319 mm Hg to 215 mm Hg, th volume changes from 0.55

Dmitry_Shevchenko [17]

In this question we need to find the new volume of the gas. Since we have been given the pressure and temperature change, we can used to combined gas law equation.
$\frac{P1V1}{T1} = \frac{P2V2}{T2}$
the parameters for 1st instance are given on the left side and parameters for the second instance are given on the right side of the equation
(319 mmHg x 0.558 L)/ 115 K = (215 mmHg x V)/387 K
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7 0

2 years ago

Read 2 more answers

495 cm3 of oxygen gas and 877 cm3 of nitrogen gas, both at 25.0 C and 114.7 kpa, are injected into an evacuated 536 cm3 flask. F

I am Lyosha [343]

Answer:

Total pressure of the flask is 2.8999 atm.

Explanation:

Given data:

Volume of oxygen (O2) gas= 495 cm3

= 0.495 L (1 cm³ = 1 mL = 0.001 L)

Volume of nitrogen (N2) gas = 877 cm3

= 0.877 L (1 cm³ = 1 mL = 0.001 L)

volume of falsk = 536 cm3

= 0.536 L (1 cm³ = 1 mL = 0.001 L)

Temperature = 25 °C

T = (25°C + 273.15) K

= 298.15 K

Pressure = 114.7 kPa

= 114.700 Pa

Pressure (torr) = 114,700 / 101325

= 1.132 atm

Formula:

PV=nRT (ideal gas equation)

P = pressure

V = volume

R (gas constnt)= 0.0821 L.atm/K.mol

T = temperature

n = number of moles for both gases

Solution:

Firstly we will find the number of moles for oxygen and nitrogen gas.

For Oxygen:

n = PV / RT

n = 1.132 atm × 0.495 L / 0.0821 L.atm/K.mol × 298.15 K

= 0.560 / 24.47

= 0.0229 moles

For Nitrogen:

n = PV / RT

n = 1.132 atm × 0.877 / 0.0821 L.atm/K.mol × 298.15 K

n = 0.992 / 24.47

= 0.0406

Total moles = moles for oxygen gas + moles for nitrogen gas

= 0.0229 moles + 0.0406 moles

n = 0.0635 moles

Now put the values in formula

PV=nRT

P = nRT / V

P = 0.0635 × 0.0821 L.atm/K.mol × 298.15 K / 0.536 L

P = 1.554 / 0.536

P = 2.8999 atm

Total pressure in the flask is 2.8999 atm, while assuming the temperature constant.

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2 years ago

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You try to measure out exactly 5.0 milliliters of water by eye into each of five test tubes. When you go back to check the volum

jeka94

Answer:

The volumes are both, accurate and precise.

Explanation:

In the measurement of a set, precision refers to how much coincidence exists in the measurements of an specific value, as the measurements are close, we can say the volumes are precise.

Accuracy means the agreement that exists between the average of one

large series of measurements and the value of measurement

Media is 4,96 ml and I wanted to measure 5 ml. It is also close.

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2 years ago

In a particular mass of kau(cn)2, there are 6.66 × 1020 atoms of gold. What is the total number of atoms in this sample?

Vinvika [58]

Total number of atoms in the sample is the sum of number of atoms of all the elements present in the sample.

Number of gold, $Au$ atoms in $KAu(CN)_2$ = $6.66\times 10^{20}$ atoms (given)

From the formula of compound that is $KAu(CN)_2$ it is clear that the number of potassium and gold are same whereas those of carbon and nitrogen are 2 times of them.

So, the number of atoms of each element is:

Number of potassium, $K$ atoms in $KAu(CN)_2$ = $6.66\times 10^{20}$ atoms

Number of carbon, $C$ atoms in $KAu(CN)_2$ = $2\times6.66\times 10^{20}$ atoms = $13.32\times 10^{20}$

Number of nitrogen, $N$ atoms in $KAu(CN)_2$ = $2\times6.66\times 10^{20}$ atoms = $13.32\times 10^{20}$

Total number of atoms in $KAu(CN)_2$ = Number of gold, $Au$ atoms+Number of potassium, $K$ atoms +Number of carbon, $C$ atoms + Number of nitrogen, $N$ atoms

Total number of atoms in $KAu(CN)_2$ = $6.66\times 10^{20}+6.66\times 10^{20}+13.32\times 10^{20}+13.32\times 10^{20}$

Total number of atoms in $KAu(CN)_2$ = $39.96\times 10^{20}$ atoms

Hence, the total number of atoms in $KAu(CN)_2$ is $3.996\times 10^{21}$ atoms.

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2 years ago

Which of the following gives the molarity of a 17.0% by mass solution of sodium acetate, CH 3COONa (molar mass = 82.0 g/mol) in

weeeeeb [17]

Answer:

The molarity of this solution is 2.26 M (option D)

Explanation:

Step 1: Data given

Mass % = 17%

Molar mass of CH3COONa = 82.0 g/mol

Density of the solution = 1.09 g/mL

Step 2:

Assume the mass of the solution is 1.00 gram

⇒ 17.0 % CH3COONa = 0.17 grams

⇒ 83.0 % H2O = 0.83 grams

Step 3:

Density = 1.09 g/mL

Volume of the solution = total mass / density of solution

Volume of solution : 1.00 grams / 1.09 g/mL

Volume of the solution = 0.917 mL = 0.000917 L

Step 4: Calculate number of moles of CH3COONa

Number of moles = Mass / molar mass

Number of moles CH3COONa = 0.170 grams / 82.0 g/mol

Number of moles = CH3COONa = 0.00207 moles

Step 5: Calculate molarity

Molarity = moles / volume

Molarity solution = 0.00207 / 0.000917 L

Molarity solution = 2.26 mol/L = 2.26 M

The molarity of this solution is 2.26 M (option D)

6 0

2 years ago