Scientists often use controlled experiments to answer questions. Choose ALL correct statements about controlled experiments. A) No changes are made to a test group in an experiment. B) A control group is used for comparison to other groups. C) Only one change can be made per test group in an experiment. D) Changes can only be made to the control group in an experiment. E) A controlled experiment must have a control group and test group(s).

Answer:

They are symbols of elements.

Ra is the symbol of the element Radium

Ah is the symbol of the element Arrhenium

Ma  is the symbol of the element Molybdenum

Ga  is the symbol of the element Gallium

La  is the symbol of the element Lanthanum

Answer:

Ra is the symbol of the element Radium

Ah is the symbol of the element Arrhenium

Ma  is the symbol of the element Molybdenum

Ga  is the symbol of the element Gallium

La  is the symbol of the element Lanthanum

Explanation:

They are elements

Answer:

c. fluorine

Explanation:

A single replacement reaction is defined as the chemical reaction in which a strong molecule replaces the weak molecule from a compound.

In a single replacement reaction, the chloride ion in NaCl can be replaced     by fluorine and gives Sodium fluoride as fluorine (F) is stronger than chlorine (Cl) and from other given molecules also. So the single replacement reaction between NaCl and F will be:

NaCl + F2 => NaF + Cl2

Hence, the correct answer is "c. fluorine".

Answer:

Less in the top

your well wisher

Answer:

1

Explanation:

touching a metal spoon ....................water.

Explanation:

as the Hydrogen (acid) ion decreases there is a corresponding increase in the Hydroxide (basic) ion.

Answer:

a switch

Explanation:

Answer:

a switch is the answer hope it helps

Answer:

[tex]m_{Ag}=135.8gAg[/tex]

[tex]Y=88.4\%[/tex]

Explanation:

Hello there!

In this case, according to the described chemical reaction, it is possible to compute the theoretical mass of silver as mass via the 1:2 mole ratio of copper to silver and their atomic mass in the periodic table, in order to perform the following stoichiometric setup:

[tex]m_{Ag}=40.gCu*\frac{1molCu}{63.55gCu}*\frac{2molAg}{1molCu}*\frac{107.87gAg}{1molAg}\\\\ m_{Ag}=135.8gAg[/tex]

Next, given the actual yield of 120 g, we compute the percent yield via:

[tex]Y=\frac{120g}{135.8g}*100\%\\\\Y=88.4\%[/tex]

Regards!

Answer:

2.562

Explanation:

First we convert 127 g of H₂CO₃ to moles, using its molar mass:

Then we convert 800 mL to L:

Finally we can calculate the concentration of the solution as molarity:

Answer:

Helium

Explanation:

Answer:

the element is helium as it's mass number is 4 and number of electrons is equal to it's atomic no. which is 2

Answer:

4.4 mol.

Explanation:

Hello!

In this case, since the formula for calculating the molarity is:

[tex]M=n/V[/tex]

Whereas n stands for moles and V for the volume in liters; we can solve for n as shown below when we are given the volume and the molarity:

[tex]n=V*M[/tex]

Thus, we plug in the given data to obtain:

[tex]n=2.5L*1.75mol/L=4.4mol[/tex]

Best regards!

Answer:

4.4 mol.

Explanation:

Have a great day

Answer:

A 70%

B 92%

C 87%

D 79%

Explanation:

This excercise is about dividing water by liquid.

Answer:

AU9NJ-BLVHV-TCLJS-54YTB

Answer:

K^2O

Explanation:

I remember a question like this one and I got it right its K^2O

(aka its C)

oops...  sorry...  I need to delete this response.  I was trying to answer a different question,

Answer:

it should be C. the filtering of ground water. have a good day!

Answer:

1: f 2: b 3: d 4: e 5:a 6:c

Explanation:

Answer: 22.3 *10^23 S atoms

Explanation:

Answer:

Georgia and minessota

Explanation:

they have no production

Answer:

4.584*10^23 molecules

Explanation:

Find molar mass of nitrogen and oxygen on periodic table.

find molar mass of nitrogen dioxide

use this to find moles of nitrogen dioxide

multiply by avagadros number

Answer:

83.7% oxygen, 16.3% hydrogen

Explanation:

Mass of compound = 16.75 g

Mass of Oxygen = 14.02 g

Mass of Hydrogen =  2.73 g

Percentage composition = Mass of element /  Mass of compound    100%

Percentage composition of Oxygen = 14.02 g / 16.75 g    * 100%

Percentage composition of Oxygen = 0.837 * 100 = 83.7%

Percentage composition of Hydrogen = 2.73 g / 16.75 g    * 100%

Percentage composition of Hydrogen = 0.163 * 100 = 16.3%

The correct option is;

83.7% oxygen, 16.3% hydrogen

Answer:

83.7% oxygen, 16.3% hydrogen

Explanation:

To determine the percent composition we can divide, our mass by total mass and afterwards, multiply by 100.

(Mass of O / Total mass) . 100 = % O

(Mass of H / Total mass) . 100 = % H

Remember that:

% O + % H = 100

Mass of O / Total mass + Mass of H / Total mass = 1

(14.02 g / 16.75g) . 100 = 83.7 %

(2.73 g /16.75g) . 100 = 16.3 %

Answer:

Equilibrium constant, Kc = 0.023

Explanation:

Equation for the decomposition of Hydrogen iodide is given below:

2HI ----> H₂ + I₂

Initially, the number of moles of the reactant and the products are given as follows:

n(HI) = 2 * 3.800 moles = 7.600 moles

nH₂) = 0.000 moles

n(I₂) = 0.000 moles

At equilibrium, the equation becomes: 2HI <----> H₂ + I₂

Number of moles of the reactant and the products are given as follows:

n(HI) = 7.600 - (0.886 + 0.886) moles = 5.828 moles

nH₂) = 2 * 0.443 = 0.886 moles

n(I₂) = 2 * 0.443 = 0.886 moles

Equilibrium constant, Kc = [H₂] [I₂] / [HI]²

Equilibrium constant, Kc = (0.886) * (0.886) / (5.828)²

Equilibrium constant, Kc = 0.023

Answer:

1 and the element is hydrogen (there is an exception for the octet rule for the element hydrogen) hope this helps

Explanation:

Answer: B. It must show that the mass of each element involved is conserved  by a chemical reaction.

Explanation:

According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.

The correct statement why a chemical equation must be balanced is It must show that the mass of each element involved is conserved  by a chemical reaction.

Answer:

B. It must show that the mass of each element involved is conserved

by a chemical reaction.

Explanation:

a p e x, just took the quiz

Answer:

ΔH = -44.029 KJ/mol

Explanation:

We are told that 60.0 g of NaOH is dissolved in one litre of water.

From conversion, 1 litre = 1000 g

From tables, specific heat capacity of water; c = 4.18 J/g/°C

We are given ΔT = 15.8 °C

Formula for the heat absorbed by the solution is given as;

Q = mcΔT

Where;

Q = Heat gained by the water

m = Mass of the water

c = Specific heat of water

ΔT = change in temperature

Thus;

Q = 1000 × 4.18 × 15.8

Q = 66044 J

The solution absorbed 66044 J and therefore it means that the dissolution of the salt gave off 66044 J.

Thus;

Enthalpy is; ΔH = -66044 J

Now, Mass of NaOH is 60 g.

We know that molar Mass of NaOH is 39.997 g/mol. Thus;

Converting to moles, we have;

n = 60/39.997

n = 1.5 mol

Now, enthalpy when 1.5 moles of NaOH are dissolved in water will be;

ΔH = -66044 J/1.5 moles

ΔH = -44029.33 J/mol

ΔH = -44.029 KJ/mol

Answer:

a

Explanation:

Answer:

zoo wee mama

Explanation:

The particles that make up an object are held together by bonds. Insulators have strong bonds that hold their particles rigidly in place. This prevents particles from gaining energy and increasing the temperature. Wool, dry air, plastics, and polystyrene foam are all examples of good insulators.

Answer:

Zn + 2HCl → ZnCl₂ + H₂

Explanation:

First we write the equation using the molecular formulas instead of words:

We know zinc chloride is ZnCl₂ as the problem tells us the oxidation state of zinc in the products is +2, and chloride means Cl⁻¹.

Now we proceed to balance the reaction:

There are 2 Cl atoms and 2 H atoms on the right side, so we add a coefficient of 2 to HCl on the left side:

Answer:

7.40×10²² molecules.

Explanation:

From the question given above, the following data were obtained:

Volume of oxygen = 2.75 L

Number of molecules of oxygen =?

Next, we shall determine the number of mole of oxygen present. This can be obtained as follow:

22.4 L contains 1 mole of oxygen at STP.

Therefore, 2.75 L will contain = 2.75 / 22.4 = 0.123 mole of oxygen at STP.

Finally, we shall determine the number of molecules of oxygen present. This can be obtained as follow:

From Avogadro's hypothesis:

1 mole of oxygen = 6.02×10²³ molecules

Therefore,

0.123 mole of oxygen = 0.123 × 6.02×10²³

0.123 mole of oxygen = 7.40×10²² molecules.

Thus, the cylinder contains 7.40×10²² molecules of oxygen.