statement, \"In a chemical reaction, matter is neither created nor destroyed\" i

Question

statement, "In a chemical reaction, matter is neither created nor destroyed" is called A) the Law of Conservation of Mass B) the Law of Definite Proportions. C) the Scientific Method D) the Law of Multiple Proportions. E) Dalton's Atomic Theory 9) The 10) Without using a calculator, solve the following problem: 10) 1105)(1 102)]2 (1 10-10) A) 1 10-6 B) 1 1034 D) 1 × 1024 11) Round off 00507506 to four significant figures A) 5100 B) 5076 C) 0051 D) 5.075105 12) A substance that can't be chemically broken down into simpler substances is A) a compound B) an element. C) an electron D) a heterogeneous mixture. E) a homogeneous mixture. 12) 13) How many cm are in 20 2 ft? A) 616 cm B) 7.95 cm C) 51.2 cm 13) D) 0.663 cm E) 242 cm 14) What does "X" represent in the following symbol? 28 14 14) A) ruthenium B) zinc C) sulfur D) silicon E) nicke 15) Identify a cation. 15) A) an atom that has gained an electron C) an atom that has lost a proton B) an atom that has gained a neutrorn D) an atom that has lost an electron 16) Which of the following elements is a alkali metal? 16) A) Ca B) U 17) Isotopes differ in the number of 17) A) neutrons. B) electrons C) neutrons and protons D) gamma particles. E) compounds

Explanation / Answer

Solution:- (9) It's choice A) The law of conservation of mass which states that mass could neither be created nor destroyed.

(10) [(1 x 105) x (1 x 102)]2/(1 x 10-10)

In multiply, the exponents are added. so, 5 + 2 = 7 That means for the numerator we get (1 x 107)2

Square means multiply a number by itself. So, (1 x 107)2 = 1 x 107 x 1 x 107 = 1 x 1014

Now, 1 x 1014/ 1 x 10-10

in division, exponents are subtracted.

so, 14 - (-10) = 24

hence, the final answer is 1 x 1024. Choice D) is the right one.

(11) we need to round 00507506 to four sig figs. Sor this we need to make the last six 0 as the ending zeros are not sig figs if there is not a decimal place in the number.

So, it would be 0.00507500, in scientific notations it could be written as 5.075 x 105. So, choice D is the correct one.

(12) It's an element that could not be further broken down chemically. For example Fe is an Iron element that could further not be broken chemically. So, the correct choice is B) an element.

(13) 1 ft = 12 in

1 in = 2.54 cm

So, 20.2 ft x (12 in/1ft) x (2.54 cm/1in) = 616 cm

(14) The given elemental symbol is 14X28.

the lower case number is the atomic number and the upper case number is mass number.

In periodic table, elements are placed on the basis of their atomic numbers.

Looking at the periodic table, element with atomic number 14 is Silicon, Si.

D is the right choice.

(15) cation is an ion with positive charge. When an atom loses electron it forms a cation.

For example, Na -----> Na+ + e-

Na+ is the cation.

So, D is the right choice.

(16) Elements present in first group of periodic table are known as alkali metals. Looking at the given choices, K(potassium) is the alkali metal.

So, the right choice is D.

(17) Isotopes are the elements having with equal number of protons but different number of neutrons.

For example, 1H1, 1H2 and 1H3 are the three isotpes of hydrogen.

All these have 1 proton but the number of neutrons are 0, 1 and 2 respectively.

A( is the right choice.

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