Select the correct answer.

Elements that can be very dangerous but form useful materials when combined with other elements

ELEN [110]

Answer: Halogens

Explanation:

Halogens include elements like Fluorine, Chlorine, Iodine and Bromine. These elements can be dangerous to humans especially when used in large quantities.

When combined with other elements however, they can form very useful materials. Chlorine for instance forms salt when combined with sodium. Fluorine becomes very useful in toothpaste to protect teeth and bromine can be used in pesticides.

6 0

3 years ago

2. Circle all of the following that change with the temperature of a reaction.

sergey [27]

The activation energy (Ea) for the reaction is calculated from the slope as is - 1.16kJ.

<h3>What the Arrhenius equation?</h3>

The Arrhenius equation relates the rate constant of a reaction to the temperature of the reaction. It is an offshoot of the collision theory. We must note that the collision factor A is the y intercept of the graph.

Given that T = -350 K

R = 8.314 J/K.mol

Ea = ??

-350 = Ea/8.314

Ea = -350 × 8.314

Ea = - 1.16kJ

Learn more about activation energy:brainly.com/question/11334504

6 0

2 years ago

In the reaction CuO(s) + CO2(g) → CuCO3(s), a. CO2 is the Lewis acid and CuCO3 is its conjugate base. b. O2– acts as a Lewis bas

adoni [48]

<u>Answer:</u> The correct answer is Option d.

<u>Explanation:</u>

According to Lewis acid-base concept:

The substance which is donating electron pair is considered as Lewis base and the substance which is accepting electron pair is considered as Lewis acid.

For the given chemical reaction:

$CuO(s)+CO_2(g)\rightarrow CuCO_3(s)$

$CO_2$ is accepting electron pair and is getting converted to $CO_3^{2-}$ . Thus, it is considered as Lewis acid.

$O^{2-}$ present in CuO is a Lewis base because it is donating electron pair.

Thus, the correct answer is Option d.

4 0

3 years ago

10.0 g Cu, C Cu = 0.385 J/g°C 10.0 g Al, C Al = 0.903 J/g°C 10.0 g ethanol, Methanol = 2.42 J/g°C 10.0 g H2O, CH2O = 4.18 J/g°C

Mazyrski [523]

Answer:

Lead shows the greatest temperature change upon absorbing 100.0 J of heat.

Explanation:

$Q=mc\Delte T$

Q = Energy gained or lost by the substance

m = mass of the substance

c = specific heat of the substance

ΔT = change in temperature

1) 10.0 g of copper

Q = 100.0 J (positive means that heat is gained)

m = 10.0 g

Specific heat of the copper = c = 0.385 J/g°C

$\Delta T=\frac{Q}{mc}$

$=\frac{100.0 J}{10 g\times 0.385J/g^oC}=25.97^oC$

2) 10.0 g of aluminium

Q = 100.0 J (positive means that heat is gained)

m = 10.0 g

Specific heat of the aluminium= c = 0.903 J/g°C

$\Delta T=\frac{Q}{mc}$

$=\frac{100.0 J}{10 g\times 0.903 J/g^oC}=11.07^oC$

3) 10.0 g of ethanol

Q = 100.0 J (positive means that heat is gained)

m = 10.0 g

Specific heat of the ethanol= c = 2.42 J/g°C

$\Delta T=\frac{Q}{mc}$

$=\frac{100.0 J}{10 g\times 2.42 J/g^oC}=4.13 ^oC$

4) 10.0 g of water

Q = 100.0 J (positive means that heat is gained)

m = 10.0 g

Specific heat of the water = c = 4.18J/g°C

$\Delta T=\frac{Q}{mc}$

$=\frac{100.0 J}{10 g\times 4.18 J/g^oC}=2.39 ^oC$

5) 10.0 g of lead

Q = 100.0 J (positive means that heat is gained)

m = 10.0 g

Specific heat of the lead= c = 0.128 J/g°C

$\Delta T=\frac{Q}{mc}$

$=\frac{100.0 J}{10 g\times 0.128 J/g^oC}=78.125^oC$

Lead shows the greatest temperature change upon absorbing 100.0 J of heat.

3 0

4 years ago

The masses of four objects are given in this table. If all of the objects have the same acceleration, which will require the gre

worty [1.4K]

Answer:

Object 4 in the example

Explanation:

For simplicity and a clearer view of this problem, let's assume that four masses from 1 to 4 have the the masses 2 kg, 4 kg, 6 kg, 8 kg respectively.

According to the second Newton's law, we know that force is directly proportional to both mass and acceleration. The equation representing this is $F = ma$ .

Notice that all of them have the same acceleration. This means, the greater the mass, the greater the force for a fixed acceleration. Simply speaking, the forces for each of the objects would be 2a, 4a, 6a and 8a respectively.

Since we're interested in the magnitude of the force and not direction, we neglect whether acceleration is positive or negative. This means that object 4 will require the greatest force to move, as it has the greatest mass.

3 0

3 years ago