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3 years ago

When substances are formed that are different from the starting substances, a physical change has occurred. True False

2 answers:

4 0

False, because physical change does not involve the formation of substances. An example of physical change is change of state e.g water freezing .It is still water if you were to melt it.

Strike441 [17]3 years ago

3 0

Answer: The given statement is false.

Explanation:

Chemical change is defined as a change in which chemical composition and chemical properties of a substances changes.

For example: Rust formation on the iron.

Physical change is defined as a change in which form of the substance changes while chemical composition remains unchanged.

For example: Melting of an ice.

Here, new substance is formed which is different from the starting substance which means that a chemical change occurred.

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Which substance has a coefficient of 2 when you balance the equation for this redox reaction? cu(s) + hno3(aq) → cu(no3)2(aq) +

Mama L [17]

In this redox reaction, the Cu goes from oxidation state of (0) to (+2), therefore it oxidises. N in HNO₃ goes from oxidation state of (+5) to N in NO with oxidation state of (+2) and becomes reduced.
Cu acts as the reducing reagent and HNO₃ is the oxidising agent.
oxidation half reaction
Cu ---> Cu²⁺ + 2e --1)
reduction half reaction
4H⁺ + 3e + NO₃⁻ ---> NO + 2H₂O --2)
to balance the number of electrons , 1) x3 and 2) x2
3Cu ---> 3Cu²⁺ + 6e
8H⁺ + 6e + 2NO₃⁻ ---> 2NO + 4H₂O
add the 2 equations
3Cu + 8H⁺ + 2NO₃⁻ ---> 3Cu²⁺ + 2NO + 4H₂O
add 6 nitrate ions to both sides to add up to 8 and form acid with 8H⁺ ions
3Cu + 8HNO₃ ---> 3Cu(NO₃)₂ + 2NO + 4H₂O
Balanced equation for the redox reaction is as follows;
3Cu(s) + 8HNO₃(aq) → 3Cu(NO₃)₂(aq) + 2NO(g) + 4H₂O(l)

NO has a coefficient of 2

8 0

3 years ago

Which feature of four different marine fossils makes the fossil organism most similar to the present-day organism with four limb

zvonat [6]

I found the rest of the exercise on the internet and these are the options.
"-Undifferentiated vertebrae throughout the body.
-One neck vertebra allowing up and down movement.
-Many neck vertebrae that allow for greater mobility.
-Two neck vertebrae allowing up and down and sideways movement."

The correct answer would be the third. - "Many neck vertebrae that allow for greater mobility." The present-day organism with four limbs has a neck with several vertebrae that allow movements of rotation (mostly because of only two vertebrae at the top of the neck), and side way movements, as well as back and forth movements.

6 0

3 years ago

In the reaction 2 H2 + O2m 2 H20, how

Tresset [83]

Answer:

Option F. 3moles

Explanation:

The equation for the reaction is given below:

2H2 + O2 —> 2H2O

from the equation,

2moles of H2 required 1mole of O2.

Therefore, 6moles of H2 will require = 6/2 = 3moles of O2

8 0

3 years ago

Read 2 more answers

Which elements consists of a metal a matalloid and a noble gas

maw [93]

The answer is sodium silicon and argon

4 0

3 years ago

Hydrogen and oxygen react chemically to form water how much water would form if 14.8grams of hydrogen reacted with 34.8 grams of

pishuonlain [190]

Answer:

There will be formed 39.1935 grams H2O formed

Explanation:

Step 1: The balanced equation

2H2 + 02 → 2H20

Step 2: Given data

mass of hydrogen = 14.8 grams

Molar mass of hydrogen = 2.02 g/mole

mass of oxygen = 34.8 grams

Molar mass of oxygen = 32 g/mole

Step 3: Calculate moles

moles = mass / Molar mass

moles of hydrogen = 14.8g/ 2.02 g/mole = 7.33 moles

moles of oxygen = 34.8g / 32g/mole = 1.0875 moles

For 2 moles hydrogen consumed, we need 1 mole of oxygen.

This means oxygen is the limiting reagens and will be consumed completely. Hydrogen is the reactant in excess, there will remain 5.155 moles of hydrogen

Step 4: Calculate moles of H2O

We see that for 2 moles of H2 consumed, there is needed 1 mole of O2, to produce 2 moles of H2O.

For 1.0875 moles of oxygen consumed, there will be produced 2.175 moles of H2O

Step 5: Calculate mass of water

Mass of H2O = moles of H2O * Molar mass of H2O

Mass of H2O = 2.175 moles * 18.02 g/moles 39.1935 grams

There will be formed 39.1935 grams H2O formed

4 0

3 years ago