1.
Which of the following statements is true concerning acids and bases
Correct Answer
B. Acids mixed with bases neutralize each other
Explanation
When acids and bases are mixed together, they undergo a chemical reaction called neutralization. In this reaction, the acidic properties of the acid and the basic properties of the base cancel each other out, resulting in the formation of a salt and water. This process leads to the neutralization of both the acid and the base, hence the statement that acids mixed with bases neutralize each other is true.
2.
True or false: bases are sometimes called alkalis.
Correct Answer
A. True
Explanation
Bases are sometimes called alkalis because alkalis are a subset of bases. Alkalis are bases that are soluble in water and produce hydroxide ions (OH-) when dissolved. Bases, on the other hand, are substances that can accept protons or donate pairs of electrons. Therefore, all alkalis are bases, but not all bases are alkalis.
3.
Which is the correct set of acid properties
Correct Answer
B. Sour taste, corrosive, change litmus from blue to red
Explanation
The correct set of acid properties is sour taste, corrosive, and change litmus from blue to red. Acids typically have a sour taste, can cause corrosion or damage to certain materials, and can change the color of litmus paper from blue to red.
4.
A Netral solution has a pH of ______?
Correct Answer
7
seven
Explanation
A neutral solution has a pH of 7. The pH scale measures the acidity or alkalinity of a solution, with values below 7 being acidic, 7 being neutral, and values above 7 being alkaline. Therefore, a pH of 7 indicates that the solution is neither acidic nor alkaline, making it neutral. The word "seven" is simply another way of expressing the numerical value of 7.
5.
What does pH measure?
Correct Answer
A. The amount of H+ ions in a solution
Explanation
pH measures the concentration of hydrogen ions (H+) in a solution. It indicates the acidity or alkalinity of a solution, with a pH below 7 being acidic, a pH of 7 being neutral, and a pH above 7 being alkaline. The more H+ ions present, the lower the pH value, indicating a higher acidity. Therefore, the correct answer is "The amount of H+ ions in a solution."
6.
pH of less than 7 is basic; pH of more than 7 is acidic
Correct Answer
B. False
Explanation
The statement is false because it incorrectly states that a pH of less than 7 is basic and a pH of more than 7 is acidic. In reality, a pH of less than 7 is acidic, while a pH of more than 7 is basic. The pH scale ranges from 0 to 14, with 7 being neutral. A pH below 7 indicates an acidic solution, while a pH above 7 indicates a basic (alkaline) solution.
7.
If a substance has more OH- ions it is considered a ___________ ?
Correct Answer
B. Base
Explanation
If a substance has more OH- ions, it is considered a base. This is because bases are substances that can accept protons (H+ ions) or donate hydroxide ions (OH- ions). The presence of more OH- ions indicates a higher concentration of hydroxide ions, which is a characteristic of bases.
8.
When an acid reacts with a metal it will always produce:
Correct Answer
A. Hydrogen Gas + Salt
Explanation
When an acid reacts with a metal, it will always produce hydrogen gas and salt. This is because acids are substances that release hydrogen ions (H+) when dissolved in water, and metals are substances that can donate electrons. The reaction between an acid and a metal involves the transfer of electrons from the metal to the hydrogen ions in the acid, resulting in the formation of hydrogen gas (H2) and a salt compound. This reaction is commonly known as a metal-acid reaction or a single displacement reaction.
9.
When an acid reacts with a base it will always produce:
Correct Answer
C. Salt + Water
Explanation
When an acid reacts with a base, it forms a neutralization reaction. This reaction results in the formation of salt and water. The acid donates a proton (H+) to the base, forming water, and the remaining ions from the acid and base combine to form a salt. Therefore, the correct answer is "Salt + Water."
10.
When an acid reacts with a Carbonate it will always produce:
Correct Answer
B. Carbon Dioxide + Water + Salt
Explanation
When an acid reacts with a carbonate, it will always produce carbon dioxide, water, and salt. This is because the acid reacts with the carbonate ion (CO3 2-) to form carbon dioxide gas (CO2), water (H2O), and a salt compound. The reaction is a double displacement reaction, where the carbonate ion is replaced by the acid, resulting in the formation of carbon dioxide and water as byproducts. The salt compound is formed from the combination of the remaining ions from the acid and the carbonate.
11.
Complete the reaction:
Hydrocholric Acid + Magnesium -> Hydrogen Gas + _____________
Correct Answer
C. Magnesium Chloride
Explanation
When hydrochloric acid reacts with magnesium, it forms magnesium chloride and hydrogen gas. This is a typical example of a single displacement reaction, where magnesium replaces hydrogen in the hydrochloric acid to form magnesium chloride.
12.
Complete the reaction:
Nitric Acid + Calcium Carbonate -> Water + ____________ + _______________
Correct Answer
A. Carbon Dioxide + Calcium Nitrate
Explanation
When nitric acid reacts with calcium carbonate, it produces carbon dioxide and calcium nitrate as the products. This can be represented by the balanced chemical equation: HNO3 + CaCO3 -> CO2 + Ca(NO3)2.
13.
Sulfuric Acid + Sodium Hydroxide -> _____________ + _______________
Correct Answer
C. Water + Sodium Sulfate
Explanation
When sulfuric acid reacts with sodium hydroxide, they undergo a neutralization reaction. The hydrogen ions (H+) from sulfuric acid combine with the hydroxide ions (OH-) from sodium hydroxide to form water (H2O). The remaining ions, sodium (Na+) from sodium hydroxide and sulfate (SO4^2-) from sulfuric acid, combine to form sodium sulfate (Na2SO4). Therefore, the correct answer is water + sodium sulfate.
14.
Adding an Acid to a Base is called
Correct Answer
D. Neutralisation
Explanation
When an acid is added to a base, it results in a chemical reaction known as neutralization. In this reaction, the acidic and basic properties of the substances are neutralized, leading to the formation of water and a salt. The pH level of the solution becomes closer to 7, indicating a neutral state. Therefore, the correct answer is "Neutralisation".
15.
What is an indicator?
Correct Answer
C. Any substance that changes colour over different pH levels
Explanation
An indicator is a substance that changes color over different pH levels. This means that when an indicator comes into contact with an acidic or basic solution, it undergoes a color change. This color change can be used to determine the pH of a solution, as different indicators have different color ranges and will change color at different pH levels. Therefore, an indicator is not just any substance that changes color, but specifically a substance that changes color in response to changes in pH.
16.
What are some of the disadvantages of using an indicator?
Correct Answer
A. Colour changes may not be easy to see
Explanation
The disadvantage of using an indicator is that the color changes may not be easy to see. This means that it may be difficult to accurately determine the endpoint of a reaction or the presence of a certain substance. This can lead to inaccurate results and affect the overall reliability of the experiment or analysis being conducted.
17.
Examine the image below of colour changes using universal indicator:
What colour indicates a very strong acid?
Correct Answer
B. Orange
Explanation
The colour orange indicates a very strong acid. This is because universal indicator is a pH indicator that changes colour based on the acidity or alkalinity of a solution. Orange is typically associated with a pH level of around 3-4, which is considered highly acidic. Therefore, the orange colour in the image suggests that the solution being tested is a very strong acid.
18.
How can you test for Hydrogen gas, after reacting an acid and a metal?
Correct Answer
C. Light a match and insert it into the test-tube
Explanation
By lighting a match and inserting it into the test-tube, you can test for the presence of Hydrogen gas. Hydrogen is highly flammable, so if it is present in the test-tube, it will react with the flame and produce a small explosion or a popping sound. This confirms the presence of Hydrogen gas.
19.
Examine the image below of colour changes using universal indicator:
Which colour indicates a very strong Base?
Correct Answer
C. Purple
Explanation
Purple indicates a very strong base. In the universal indicator scale, purple represents a high pH level, indicating a strong alkaline or basic substance. As the pH scale ranges from 0 to 14, with 0 being highly acidic and 14 being highly basic, purple falls towards the higher end of the scale, indicating a strong base.
20.
Lemons, Vinegar and Yoghurt are all exaples of _________?
Correct Answer
A. Acids
Explanation
Lemons, vinegar, and yogurt are all examples of acids because they contain acidic properties. Acids are substances that have a pH level below 7 and can donate hydrogen ions in a chemical reaction. These three items, when consumed or used in cooking, can add a sour taste to food due to their acidic nature.