During an experiment, Mr. Lehman tells his students to be alert for signs that an endothermic reaction is happening. Which of the following scenarios would his students most likely observe?

Answers

Answer 1

Answer: The correct answer for the question that is being presented above is this one: "A test tube becomes cool to the touch." During an experiment, Mr. Lehman tells his students to be alert for signs that an endothermic reaction is happening. The student will most likely observed that the test tube becomes cool to the touch.

Answer 2

Answer:

Answer:

these are the choices

Explanation:

1 A test tube becomes cool to the touch.

2 A liquid appears to glow.

3 A new odor comes from a beaker.

4 A solid forms from a mixture of solutions.

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Which solution will change litmus paper red?B) CH300 (aq)A) NaOH (aq)How many milliliters 0.100 M NaoH(aq) would be needed to compofB) 50.0 mLA) 300. mL

Answers

None of the solutions will change the litmus paper to red. Normally, a litmus paper is colored blue and when acidic solution is present it will turn to red. Since the given choices are CH3OO- (Acetate Ion) and NaOH (Sodium Hydroxide) are both base.

HELP ME with THIS I am time i have a little bit of time and still have more questions !!! CHEMISTRY!!

Answers

Answer:

1. is B 2. is C or B

Explanation:

How many grams of CaCl₂ should be dissolved in 500.0 mL of water to make a 0.20M solution of CaCl₂?

Answers

0.2M means 0.2mol CaCl2/1L solution.

This question didn't give us a density of the solution so needs an assumption that the solution has equal volume to water.

xmol/0.5L=0.2M
x = 0.1

0.1mol of CaCl2 is needed. Ca=40g/mol, Cl=35.5g/mol.
CaCl2 0.1mol = (40+35.5*2)*0.1=11.1g

Which of the following cn be observed when 20,0 of 1.0 M NaOH (aq), 10.0 mL of 1.0 M HCL(aq), and a few drops of phenolphthalein are combined and react?

Answers

Answer:

The final solution will be clear and colorless.

Explanation:

The balanced reaction equation is:

NaOH + HCl ⇒ H₂O + NaCl

The amount of NaOH that is added is calculated as follows:

(20.0mL)(1.0mol/L) = 20 mmol NaOH

Similarly, the amount of HCl that is added is as follows:

(10.0mL)(1.0mol/L) = 10 mmol HCl

Since HCl and NaOH react in 1:1 proportions, the HCl is the limiting reaction. 10 mmmol of HCl will neutralize 10 mmol of NaOH, leaving 10 mmol of NaOH. The volume of the mixed solution is 30.0 mL, so the concentration of NaOH in the final solution is:

(10 mmol)/(30.0mL) = 0.3333 M NaOH

The pOH of the final solution is:

pOH = -log([OH⁻) = -log(0.3333) = 0.477

The pOH is related to the pH as follows:

pH = 14 - pOH = 14 - 0.477 = 13.5

At a pH of 13.5, phenolphthalein is colorless. The final solution will be observed as clear and colorless.

How can there be more than 1000 different atoms when there are only about 100 different elements?

Answers

Actually, there are only about 100 atoms that have been yet discovered. But each element has many different kinds of atom. For instance, carbon. Do you know carbon has more than 30 or 50 different types of atoms? Well, how? There are isotopes. Don't think that there is only one carbon atom which has 6 electrons and 6 protons and 6 neutrons. There are more. C-13 has 6 electrons and 6 protons and 7 neutrons. While, C-14 has 6 electrons and 6 protons and 8 neutrons. I just showed you three stable isotopes of carbon(element). But, what is really an isotope?? Did you notice that all of these atoms had the same number of protons and electron but different numbers of neutrons? This is really an isotope. Well, if an atom takes a few more electrons or gives off a few electrons, it still stays the same element/ atom type. Just like that an element can have atoms of different neutron number. It may be less or more. It doesn't affect the atom much: just makes an isotope. But it does affect the atomic mass number or radioactivity of an atom. So, an element can have many different forms of isotopes of its atoms. In this way, being only 100 atoms, there can 1000 atoms or (more than that!).

To make it more clear-

Definition of ISOTOPE: any of two or more forms of a chemical element, having the same number of protons and electrons in the nucleus, or the same atomic number, but having different numbers of neutrons

HOPE YOU UNDERSTOOD THE MATTER:-))

There can be more atoms because atoms make about everything and those atoms make up the elements and since,atoms are in everything there can be different kinds of atoms to make up certain things.

When two intermediate chemical equations are combined, the same substance that appears in the same phase can be canceled out, provided thatA) it is a reactant in one intermediate reaction and a catalyst in the other reaction.
B) it is a product in one intermediate reaction and a catalyst in the other reaction.
C) it is a reactant in one intermediate reaction and a product in the other reaction.
D) it is a reactant in both of the intermediate reactions.

Answers

Answer: Option (C) is the correct option.

Explanation:

When two intermediate chemical equations are combined, the same substance that appears in the same phase can be canceled out, provided that it is a reactant in one intermediate reaction and a product in the other reaction.

For example,

$2Al(s) + 2KOH(aq) + 6H_(2)O\rightarrow 2KAl(OH)_(4)(aq)+ 3H_(2)(g)$ ....(1)

$2KAl(OH)_(4)(aq) + 4H_(2)SO_(4)(aq) + 6H_(2)O(l)\rightarrow 2KAl(SO_(4))_(2)(aq)+ 12H_(2)O(s)$ .........(2)

Cancelling the common species in both the equations as follows.

$2Al(s) + 2KOH(aq) + 6H_(2)O\rightarrow \not{2KAl(OH)_(4)(aq)}+ 3H_(2)(g)$

$\not{2KAl(OH)_(4)(aq)}+ 4H_(2)SO_(4)(aq) + 6H_(2)O(l)\rightarrow 2KAl(SO_(4))_(2)(aq)+ 12H_(2)O(s)$

Therefore, on addition we get the equation as follows.

$2Al(s)+ 2KOH(aq) + 4H_(2)SO_(4)(aq) + 22H_(2)O(l)\rightarrow 3H_(2)(g)+ 2KAl(SO_(4))_(2) + 12H_(2)O(s)$

The right answer for the question that is being asked and shown above is that: "C) it is a reactant in one intermediate reaction and a product in the other reaction." When two intermediate chemical equations are combined, the same substance that appears in the same phase can be canceled out, provided that it is a reactant in one intermediate reaction and a product in the other reaction.

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