Which of the following statements is true about chemical reactions? endothermic reactions absorb heat and exothermic reactions give off heat

exothermic reactions absorb heat and endothermic reactions give off heat

endothermic and exothermic reactions absorb heat

endothermic and exothermic reactions give off heat

Answers

Answer 1

Answer: Endothermic reactions absorb heat and exothermic reactions give off heat

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The pH is a solution remains constant in the presence of a buffer if acid or base is added beyond the buffer capacity. True or false.

Answers

The strong acid and strong base has high rate constant of dissociation. Weak acid and base are the one whose rate constant for the dissociation is low, they do not dissociate readily in water. Therefore, the given statement is false.

What are acid and base?

Acid is a solution which releases H⁺ hydrogen ion when dissolved in water. Base are the solution which releases hydroxide ion OH⁻ ion when dissolved in water. pH is measurement of hydronium ion.

A buffer is a solution containing either a weak acid and its salt or a weak base and its salt, which is resistant to changes in pH. The statement is false. When you add an acid or base in amounts greater than the buffer capacity you no longer have the buffer to influence solution pH.

Therefore, the given statement is false.

To know more about acid and bases, here:

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The answer is false. When you add an acid or base in amounts greater than the buffer capacity you no longer have the buffer to influence solution pH

Which of the answer choices accurately describes a trend that occurs when moving left to right across periods?(Select all that apply.)

reactivity increases
atomic radius increases
atomic mass increases
valence electrons decrease

Answers

atomic radius is the correct answer

Juliet is using a paper towel to clean up a juice spill. The liquid sticks to the paper towel because of _____.adhesion
cohesion
specific heat
a neutral pH

Answers

When Juliet uses a paper towel to clean up a juice spill the liquid sticks to paper towels because of adhesion and absorption. Paper towels are made of cellulose fibres, which are made of sugar. Water molecules stick to the sugar.

Answer: Option (a) is the correct answer.

Explanation:

When molecules of different substance stick together due to force of attraction then this property is known as adhesion.

In the given situation juice sticks to the paper towel due to adhesion as it gets absorbed by the towel.

Thus, we can conclude that out of the given options, the liquid sticks to the paper towel because of adhesion.

What is the [H+] of an HCl solution if the pH is measured to be 6? Select one: a. 1 X 10-7 M b. 1 X 10-6 M c. 6 X 10-6 M d. 8 X 10-1 M

Answers

Answer : The correct option is, $1* 10^(-6)M$

Explanation : Given,

The value of pH of HCl = 6

As we know that,

pH : It is defined as the negative logarithm of hydrogen ion or hydronium ion concentration.

The formula of pH is :

$pH=-\log [H^+]$

Now put all the given values in this formula, we get the concentration of hydrogen ion.

$6=-\log [H^+]$

$[H^+]=1* 10^(-6)M$

Therefore, the concentration of hydrogen ion is, $1* 10^(-6)M$

$pH=-\log_(10) [H^+] \Rightarrow [H^+]=10^(-pH) \n \npH=6 \n\ [H^+]=10^(-6)=1 * 10^(-6)$

The answer is B. 1 × 10⁻⁶ M.

Which chemicals previously used in products such as refrigerants, aerosol sprays, and cleaning products contributed to the depletion of the ozone layer

Answers

Answer:chlorofluorocarbons (CFCs) could deplete Earth's atmospheric ozone layer, which blocks the sun's damaging ultraviolet rays. When the scientists reported their findings in 1974, CFCs were widely used as refrigerant gases and as propellants in aerosol sprays

Explanation:

#1. Which statement is a correct expression of the Law of Conservation of Mass? A. The total mass is unpredictable in a chemical reaction. B. The total mass remains the same during a chemical reaction. C. The total mass decreases during a chemical reaction. D. The total mass increases in a chemical reaction. #2. Which element(s) are not balanced in this equation?Fe2O3 + 3 CO → Fe + 3 CO2

A.
Only the Fe is unbalanced.

B.
Only the O is unbalanced

C.
Fe and O are both unbalanced.

D.
C and O are both unbalanced

Answers

These are two questions and two answers.

Question 1: Law of Conservation of Mass

Answer: option B. The total mass remains the same during a chemical reaction.

Explanation:

The law of conservation of mass is a universal law. It states that mass is mass is neither created or destroyed, but is is conserved.

In chemical reactions, that means that, always, the total mass of the reactants equals the total mass of the products or, as the option B. states, during a chemical reaction the total mass remains the same.

Since, in chemical reactions, the atoms are not modified (the atoms just bond in different form or with different atoms), that implies that total number of each kind of atoms in the reactants equals the total number of the same kind of atoms in the products.

That is the basis for balancing the chemical equations and for the stoicheometric calculations.

Question 2 . Which element(s) are not balanced in this equation?

Answer: option A. Only the Fe is unbalanced.

Explanation:

1) Given equation: Fe₂O₃ + 3 CO → Fe + 3 CO₂

2) Count the number of atoms of each kind on each side of the equation

i) Fe

reactant side: 2

product side: 1

Therefore, Fe is not balanced

ii) O

reactant side: 3 + 3 = 6

Product side: 3 × 2 = 6

Therefore, it is balanced

iii) C

reactant side: 3

product side: 3

Therefore, C is balanced.

3) Conclusion: Only the Fe is unbalanced.

For #1, the answer is B. The total mass remains the same during a chemical reaction.

For #2, given Fe2O3 + 3CO -> Fe + 3CO2

Fe is unbalanced, and O is also unbalanced

Therefore, Option C: Fe and O are both unbalanced, is true.

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