S2 Homework - Holy Cross High School, ... Neutralisation Reactions 6. Acid Rain 1. The pH Scale Q1a)

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  • S2

    Homework

    Acids and Alkalis

  • This booklet is split into the main areas of the

    topic.

    Each main area has three different spice levels

    which tell you about the difficulty of the homework.

    Each week your teacher will tell

    you what main area to complete

    and you will have the choice of

    level of difficulty.

    You need make sure that you are

    trying a new spice every week!

    *A bonus Extra Hot homework may

    be found for some areas if you are feeling

    adventurous or in need of extra revision*

  • The main areas of this topic are:

    1. The pH Scale

    2. pH of food and drink

    3. Effect of Dilution

    4. Solubility of Oxides

    5. Neutralisation Reactions

    6. Acid Rain

  • 1. The pH Scale

    Q1a). Describe how you could test the pH of a solution and obtain its pH value.

    b) What colours do acids turn universal indicator?

    c) What range of pH values can be shown by acids?

    d) What colours do alkalis turn universal indicator?

    e) What range of values can be shown by alkalis?

    f) What colour do neutral solutions turn universal indicator?

    g) What is the pH value of a neutral solution?

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  • 1. The pH Scale

    As a homework exercise, pupils were asked to find the pH values of a

    number of substances. Present this information as a bar graph.

    HOUSEHOLD SUBSTANCE pH VALUE

    drain cleaner 14

    coca-cola 3

    milk 8

    window cleaner 12

    washing up liquid 7

    b) Which of these substances is the least alkaline?

    c) Which of these substances is the most acidic?

  • 1. The pH Scale

    Each statement is false. Rewrite each one as a true statement.

    a) A neutral solution has a pH of about 6.

    b) A liquid with a pH of above 7 is an acid.

    c) Universal indicator goes red in pure water.

    d) Alkalis make universal indicator turn green.

    e) Acids make universal indicator turn purple.

    f) Strong acids have a pH value equal to pH 7.

    g) As pH increases the strength of the alkali decreases.

    Q2. Copy and complete the table:

    HOME LAB

    ACIDS

    ALKALIS

  • 2.The pH of Food and Drink

    Read the passage below and answer the questions which follow.

    a) Why are preservatives added to food?

    b) Name the unsaturated acid found in some plants.

    c) Which type of compounds present in wood smoke may cause cancer?

    d) Another widely used preservative is sulphur dioxide. Try to find out examples

    of foods containing this preservative.

    e)Try to find out some examples of health problems which may arise from

    eating foods containing too many E numbers.

  • 2.The pH of Food and Drink

    The table below shows the pH of some foodstuffs.

    Food Approximate pH number

    Jelly 3.1

    Ketchup 3.6

    Mayonnaise 3.7

    Canned tomatoes 4.0

    Meats 5.2-6.9

    Soya bean milk 7.0

    Crackers 8.2

    Milk of magnesia 10.5

    a) Which food has a neutral pH value?

    b) Name a food to avoid if you already have too much acid in your stomach.

    c) Which food is the least alkaline?

    d) Which food is the most acidic?

    e) If you tested Milk of Magnesia with indicator, what colour would it go?

  • 2.The pH of Food and Drink

    2. Using the table you have just made, create a bar graph.

    3. In a paragraph, summarise the results, analysing the data.( Highest, lowest, any

    trends)

  • 3. The Effect of Dilution

    Using no more than 140 characters(including

    letters, spaces and symbols) explain what

    dilution is and how it effects the pH of acids

    and alkalis.

  • 3. The Effect of Dilution

    . Class 2C made some statements about the effect of adding

    water to an alkaline solution.

    A The pH of the solution will rise.

    B The pH of the solution will fall towards 7.

    C The solution will become more dilute.

    D Adding water will have no effect on the solution.

    a) Identify the 2 correct statements.

    b) Copy and complete the following sentences by choosing the correct

    words:

    2.i) When an acidic solution is diluted with water, the pH falls/rises and

    the acidity increases/decreases.

    2.ii) When an alkaline solution is diluted with water, the pH falls/rises

    and the alkalinity increases/decreases.

  • 3. The Effect of Dilution

    Test Tube Instructions pH number

    1 10mL of alkali

    14

    2 1mL from test

    tube 1 +9mL of

    water

    12

    3 1mL from test

    tube 1 +9mL of

    water

    10

    4 1mL from test

    tube 1 +9mL of

    water

    8

    5 1mL from test

    tube 1 +9mL of

    water

    7

    a) If test tube 1 contains 100% alkali, what % alkali is present in

    test tube 2?

    b) What is the % alkali in test tube 3 shown as a fraction?

    c) What is the trend between the % of alkali present and the pH

    number

    d) What colour would the solution in test tube 5 be once universal

    indicator is added?

  • 4. The Solubility of Oxides

    1. Copy and complete the following table:

    Name of Oxide Appearance of

    oxide

    Effect on

    Universal

    Indicator

    Carbon dioxide gas Acid

    Nitrogen dioxide gas

    Sodium oxide Solid Alkali

    Calcium oxide Solid

    Copper oxide solid

    2. What main conclusions can you draw from this table of

    results?

  • 4. The Solubility of Oxides

    1. Which of the following oxides would dissolve in water

    to produce an acidic solution?

    A. sulphur dioxide

    B. iron (III) oxide

    C. copper (II) oxide

    D. sodium oxide

    2. Which of the following oxides would dissolve in water to produce

    an alkaline solution?

    A. sulphur dioxide

    B. iron (III) oxide

    C. copper (II) oxide

    D. sodium oxide

    3. What do the following terms mean?

    a. Soluble

    b. Insoluble

    4. a) How are acids formed?

    b) How are alkaline solutions formed?

    5.Use the solutions in Q1 as an example- Draw a diagram showing

    how you would test their pH

  • 4. The Solubility of Oxides

    Using your knowledge of Science, comment on the solubility of

    oxides and the effect they can have on the environment.

    You may wish to include the terms: Non- metal oxide, Metal oxide,

    Insoluble oxides and acid rain.

  • 5. Neutralisation Reactions

    1. a)Apart from water, what is formed when an acid reacts with an

    alkali?

    b) Name the type of reaction when an acid reacts with an alkali.

    c) What happens to the pH of an acid when an alkali is added?

    d) What happens to the pH of an alkali when an acid is added?

    2. a) Explain why vinegar is added to wasp stings to soothe the pain.

    b) Explain why farmers add lime to soil which is too acidic.

  • 5. Neutralisation Reactions

    Q1. Shampoos contain different types of chemicals. The three

    main types of chemicals, and their uses, are shown in the key below.

    6. 7. 8.

    9. 10. 11.

    a) Why do cleaning chemicals in shampoo remove grease from hair?

    b) Shampoos contain chemicals to make the hair shine. Suggest a pH value

    for these chemicals.

    c) What type of compounds in shampoo would be useful for someone with

    frizzy hair?

    d) The label shows the ingredients in shampoo:

    SHAMPOO

    cleaning chemicals (usually laureth sulphates)

    conditioning chemicals (silicon containing compounds)

    shining chemicals (usually acids)

    dissolve grease stick to hair making it

    feel smooth

    makes hair surface

    smooth and reflects light

    3 in 1 Shampoo & Conditioner

    FOR ALL HAIR TYPES

    INGREDIENTS:

    Aqua, sodium laureth sulphate, hydrogenated glyceryl palmate, magnesium laureth sulphate,

    methylparben, parfume.

    75ml e

  • Identify an ingredient which could be a cleaning chemical.

    5. Neutralisation Reactions

    The following is a report given by SEPA to a fish farmer.

    Sample Date pH

    1 5th of January 7

    2 10th of March 8