Class 10th Some important questions of science

Class 10th Sami important questions of science

Q. Why does dry HCL gas not change the colour of the dry litmus paper? 
Ans. The colour of litmus paper changes only in the presence of ions like hydrogen (H+) or hydronium (H3O+) ions. 
HCl can produce these ions only in the form of aqueous solution. Hence dry HCl gas does not change the colour of dry litmus paper.

Q. Here are some results of solutions tested with universal indicator paper
Sulphuric acid:    Red
Metal polish:    Dark blue 
Washing-up liquid:    Yellow
Milk of magnesia:    Light blue
Oven cleaner:    Purple
Car battery acid:    Pink
Arrange the solutions in order of their increasing pH values (starting with the one with the lowest pH).
Ans. Sulphuric acid < car battery acid < washing up liquid < milk of magnesia < metal polish < oven cleaner 

since:
Red : pH = 1 
Pink : pH = 3-4 
Yellow: pH = 5-6 
Light blue : pH = 9 
Dark blue : pH = 10 
Purple: pH = 11

Q. (a) What would you expect the pH of pure water to be?
(b) What colour would the universal indicator show in an aqueous solution of sugar? Why?
(c) A sample of rain water turned universal indicator paper yellow. What would you expect its pH to be? Is it a strong or a weak acid?
Ans. 
(a) pH of pure water is 7.
(b) Aqueous solution of sugar will turn the color of universal indicator green because sugar solution is neutral in nature.
(c) pH of the sample of rain water will be between 5 and 6. It is a weak acid.

Q. (a) What effect does the concentration of  (aq) ions have on the nature of a solution?
(b) What effect does the concentration of  ions have on the nature of a solution?(c) Someone put some universal indicator paper into vinegar. The pH is 3. What does this tell you about the vinegar?
(d) Someone put some universal indicator paper onto wet soap. The pH is 8. What does this tell you about the soap?
(e) State whether a solution is acidic, alkaline or neutral if its pH is:
(i) 9       (ii) 4        (iii) 7       (iv) 1         (v) 10      (vi) 3
Ans. (a) As the concentration of hydrogen ions increases, the solution becomes more acidic.
(b) As the concentration of hydroxide ions increases, the solution becomes more basic.
(c) pH = 3 tell us that Vinegar is acidic in nature.
(d) pH = 8 tell us that Soap is basic in nature.
(e) Nature of the solution:
(i) pH = 9 : Alkaline.
(ii) pH = 4 : Acidic.
(iii) pH = 7 : Neutral.
(iv) pH = 1 : Acidic.
(v) pH = 10 : Alkaline.
(vi) pH = 3 : Acidic.

Q. What is the colour of a universal indicator in neutral solution?
A. Red
B. Blue
C. Greenish yellow
D. Green
Ans. 
Universal indicator is the mixture of dyes that gives different colors depending on how acidic or alkaline the solution is.
Universal indicator produces green colour in a neutral solution or at pH=7
Colour changes from yellow to pink and then to red as pH decreases from 7 to 1 (i.e in acidic medium) and it changes from blue to indigo and then to violet as pH increases from 7 to 14 (i.e.in basic solution).

Q. What happens when nitric acid is added to egg shell ? 
Ans.  Egg shells contain calcium carbonate (CaCO3). When nitric acid is added to it, brisk effervescence due to the formation of CO2 gas is observed. 
The reaction is: 
CaCO3(s) + 2HNO3 (aq)→Ca(NO3)O2(aq) + CO2(g) + H2O(l)




Comments

Post a Comment

Popular posts from this blog

CBSE Board Exam 2023 Class 10 ENGLISH (Language and Literature)

Image
Series WYXZ1/4                   Set No. 3 Q.P. Code 2/4/3 Roll No. Candidates must write the Q.P. Code on the title page of the answer-book. ENGLISH (Language and Literature) Time allowed: 3 hours Maximum Marks: 80 Note (I) Please check that this question paper contains 15 printed pages. (II) Q.P. Code given on the right hand side of the question paper should be written on the title page of the answer-book by the candidate. (III) Please check that this question paper contains 11 questions. 39 (IV) Please write down the Serial Number of the question in the answer-book before attempting it. (V) 15 minute time has been allotted to read this question paper. The question paper will be distributed at 10.15 a.m. From 10.15 a.m. to 10.30 a.m., the students will read the question paper only and will not write any answer on the answer-book during this period. General Instructions: Read the instructions very carefully and strictly foll...
Read more

Ganita Prakash Class 8 Chapter 7 Solutions Proportional Reasoning 1

Image
NCERT Class 8 Maths Chapter 7 Proportional Reasoning 1 Solutions Question Answer Ganita Prakash Class 8 Chapter 7 Solutions Proportional Reasoning 1 NCERT Class 8 Maths Ganita Prakash Chapter 7 Proportional Reasoning 1 Solutions Question Answer Example 1. (i) Are the ratios 3 : 4 and 72 : 96 proportional? (ii) What is the HCF of 72 and 96? (Page 162) Solution: (i) HCF of 3 and 4 = 1 ∴ Ratio  3 4  is in its simplest form. HCF of 72 and 96 = 24 (∵ 72 = 24 × 3 and 96 = 24 × 4) ∴  72 96 = 24 × 3 24 × 4 = 3 4 ∴ Ratio  72 96  in its simplest form is  3 4 . ∴ Ratios 3 : 4 and 72 : 96 are proportional, because both ratios in their simplest form are the same. (ii) HCF of 72 and 96 is equal to 24. Example 2. Kesang wanted to make lemonade for a celebration. She made 6 glasses of lemonade in a vessel and added 10 spoons of sugar to the drink. Her father expected more people to join the celebration. So he asked her to make 18 more glasses of lemonade. To make the lemon...
Read more

Ganita Prakash | Class 8 | Chapter 5 Number Play | Solutions

Image
Ganita Prakash | Class 8 | Chapter 5 Number Play | Solutions Ganita Prakash  Class 8  Chapter 5 Number Play Solutions  NCERT Class 8 Maths Ganita Prakash Chapter 5 Number Play Solutions Question Answer 5.1 Is This a Multiple Of? Intext Questions Q. 1. Take any 4 consecutive numbers. For example, 3, 4, 5, and 6. Place ‘+’ and signs in between the numbers. How many different possibilities exist? Write all of them. Evaluate each expression and write the result next to it. Do you notice anything interesting? (Page 112) Sol. Take the four consecutive numbers 3, 4, 5, 6. There are 3 gaps between them, and in each gap we can place either ‘+’ or ‘−’. So, total number of possibilities 2 × 2 × 2  = 2³ = 8 When four consecutive numbers are used with all possible combinations of ‘+’ and signs, the results will always be even. This is because, regardless of the sign placement, the sum will always involve adding and subtracting an equal number of consecutive numbers. S...
Read more