Which of the following properties can be used as evidence a chemical reaction has occurred? (Select all that apply)

A 151.6-g sample of a metal at 75.3°C is added to 151.6 g at 15.6°C. The temperature of the water rises to 18.9°C. Calculate the

denis-greek [22]

Answer:

4.60 J/°C g

Explanation:

This a simple calorimetry excersise. If all the heat, which is lost by the metal, is gained by the water, we assume that

Q from water = Q from metal

Q = m . C . ΔT

where C is heat capacity and ΔT, the differences between the temperatures. Let's determine the heat gained by water.

Q = 151.6 g . 4.18 J /°C g . (18.9°C - 15.6°C)

Q (+) = 2091 Joules

As this heat, was gained by the water, this heat was lost by the metal (-)

- 2091 Joules = 151.6 g . C . (Final T° - 75.3°C)

We do not know at what T° was the meta, by the end, but all the heat was gained from the water, as water was increased by 3°C, metal decreases -3°C

- 2091 Joules = 151.6 g . C . - 3°C

-2091 J / -3°C . 151.6g = 4.60 J/°C g

5 0

3 years ago

What is the name of the compound with the formula NaHCO3 ?

Marianna [84]

Answer:

Sodium bicarbonate

Explanation:

Sodium bicarbonate ( NaHCO₃ ) -

Sodium bicarbonate , according to the IUPAC nomenclature , its name is sodium hydrogen carbonate ,and in common terms also refereed to as baking soda .

It is a white crystalline solid , it is basic in nature .

<u>The cation and anion of this salt are the sodium ion ( Na⁺) and the anion bicarbonate anion (HCO³⁻) .</u>

<u />

5 0

3 years ago

How many kilowatt-hours of electricity are used to produce 3.00 kg of magnesium in theelectrolysis of molten MgCl2 with an appli

Llana [10]

Answer:

There is 29.8 kilowatt hours needed.

Explanation:

Step 1: Data given

Mass of Magnesium = 3.00 kg

Molar mass of magnesium = 24.31 g/mol

Applied emf = 4.50 V (= 4.50 J/C)

Step 2: Calculate moles of Magnesium

Moles = Mass Mg / Molar mass Mg

Moles Mg = 3000 grams / 24.31 g/mol

Moles Mg = 123.4 moles

Step 3: Calculate how many electrons are needed to produce the magnesium.

The ionic equation for the reduction of Mg^2+ :

Mg^2+ + 2e^- → Mg

Every mole of Mg requires 2 mol of electrons.

For 123.4 mol of Mg, we have 246.8 mol of electrons.

Step 3: Find how many coulombs are involved.

The Faraday constant = 96500 couloumbs

1 mole of electrons is 96500 coulombs.

246.8 mol of electrons need 2.38 *10^7 Coulombs

Step 4: Calculate kilowatt-hours of electricity needed

2.38 * 10^7 C * 4.5 J/C = 10.7 * 10^7 J

10.7 * 10^7 J * ( 1 kW-h-/ 3.6*10^6 J ) = 29.8 kWh

There is 29.8 kilowatt hours needed.

5 0

3 years ago

1. Which of these is the basic unit of mass?

jeka57 [31]

1.)B 2.)C 3.)A 4.)B 5.)C

7 0

3 years ago

Read 2 more answers

6. How many moles of water would require 92.048 kJ of heat to raise its temperature from 34.0 °C to 100.0 °C? (3 marks)

scoray [572]

Taking into account the definition of calorimetry, 0.0185 moles of water are required.

<h3>Calorimetry</h3>

Calorimetry is the measurement and calculation of the amounts of heat exchanged by a body or a system.

Sensible heat is defined as the amount of heat that a body absorbs or releases without any changes in its physical state (phase change).

So, the equation that allows to calculate heat exchanges is:

Q = c× m× ΔT

where Q is the heat exchanged by a body of mass m, made up of a specific heat substance c and where ΔT is the temperature variation.

<h3>Mass of water required</h3>

In this case, you know:

Heat= 92.048 kJ
Mass of water = ?
Initial temperature of water= 34 ºC
Final temperature of water= 100 ºC
Specific heat of water = 4.186 $\frac{J}{gC}$

Replacing in the expression to calculate heat exchanges:

92.048 kJ = 4.186 $\frac{J}{gC}$ × m× (100 °C -34 °C)

92.048 kJ = 4.186 $\frac{J}{gC}$ × m× 66 °C

m= 92.048 kJ ÷ (4.186 $\frac{J}{gC}$ × 66 °C)

<u><em>m= 0.333 grams</em></u>

<h3>Moles of water required</h3>

Being the molar mass of water 18 $\frac{g}{mole}$ , that is, the amount of mass that a substance contains in one mole, the moles of water required can be calculated as: