Question

question 27
the difference in hydrogen ion concentration between solutions with ph 4 and ph 5 is
a twofold.
b fivefold.
c tenfold.
d twentyfold.

question 28
a decomposition reaction can be symbolized by
a a + b → c + d.
b a + b → ab.
c ab → a + b.
d c + d → ab.

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Explanation:

Question 27

Step1: Recall pH formula

The formula for pH is $pH = -\log_{10}[H^+]$, where $[H^+]$ is the hydrogen ion concentration. So we can find $[H^+]$ from pH using $[H^+]=10^{-pH}$.

Step2: Calculate $[H^+]$ for pH 4

For pH = 4, $[H^+]_1 = 10^{-4}\ \text{M}$.

Step3: Calculate $[H^+]$ for pH 5

For pH = 5, $[H^+]_2 = 10^{-5}\ \text{M}$.

Step4: Find the ratio of concentrations

To find the difference in concentration, we take the ratio $\frac{[H^+]_1}{[H^+]_2}=\frac{10^{-4}}{10^{-5}} = 10$. So the concentration at pH 4 is 10 times that at pH 5.

A decomposition reaction is a type of chemical reaction where a single compound breaks down into two or more simpler substances. Let's analyze each option:

• Option A: $A + B

ightarrow C + D$ represents a double - displacement reaction (or metathesis reaction), where two reactants exchange ions or parts to form two new products.

• Option B: $A + B

ightarrow AB$ represents a combination (synthesis) reaction, where two or more substances combine to form a single product.

• Option C: $AB

ightarrow A + B$ represents a decomposition reaction, as a single compound (AB) breaks down into two simpler substances (A and B).

• Option D: $C + D

ightarrow AB$ represents a combination (synthesis) reaction, similar to option B, where two substances combine to form a single product.

Answer:

C. tenfold.

Question 28