In a heating curve, when is the temperature constant?

When a piece of zinc metal is carefully placed in a beaker of strong acid, bubbles form on the surface of the metal and begin to

kati45 [8]

Answer:

A. a new substance is being produced.

Explanation:

The bubbles most likely indicates that a new substance is being produced by this reaction. In essence, we describe this sort of change as chemical change.

In a chemical change, new substances are usually produced. They are accompanied by the evolution or absorption of energy.

The reaction of Zinc with a strong acid to produce bubbles on the surface of the metal indicates a chemical change and the formation of a new kind of substance.

Take for example, let zinc reacts with hydrocholoric acid, HCl;

Zn + 2HCl → ZnCl₂ + H₂

Since Zn is higher than Hydrogen in the activity series, it will displace it from HCl and liberate hydrogen gas as a product. This will cause the bubbles observed in the reaction.

This is a chemical change and new products have been formed.

B and D are wrong because they are both physical changes.

C is wrong because no information about such is provided by the problem statement.

So, when a piece of zinc metal combines with a strong acid, a new kind of substance is produced.

8 0

3 years ago

calculate the mass of 120cc nitrogen present at STP. how many number of molecules are present in it?

Stells [14]

Answer:

$0.15008\ \text{g}$

$3.23\times 10^{21}$

Explanation:

1 mol of nitrogen at STP = 22.4 L = 22400 cc

n = Mol of $N_2$ = $\dfrac{120}{22400}=0.00536\ \text{mol}$

M = Molar mass of $N_2$ = $28\ \text{g/mol}$

$N_A$ = Avogadro's number = $6.022\times 10^{23}\ \text{mol}^{-1}$

Mass of $N_2$ is

$m=nM\\\Rightarrow m=0.00536\times 28\\\Rightarrow m=0.15008\ \text{g}$

Mass of the nitrogen is $0.15008\ \text{g}$

Number of molecules is given by

$nN_A=0.00536\times 6.022\times 10^{23}=3.23\times 10^{21}\ \text{molecules}$

The number of molecules present in it are $3.23\times 10^{21}$

5 0

3 years ago

I need answersssss ... worth 20 POINTS!!

tester [92]

Not enough information!

Its pretty simple if you think about it.

7 0

3 years ago

Sulfur trioxide is a gas that reacts with liquid water to produce aqueous sulfuric acid, or acid rain. What is the equation for

ivanzaharov [21]

B) SO₃(g) + H₂O(l) → H₂SO₄(aq)

3 0

3 years ago

Read 2 more answers

A 17.6-g sample of ammonium carbonate contains ________ mol of ammonium ions.

postnew [5]

These problems are a bit interesting. :)

First let's write the molecular formula for ammonium carbonate.

NH4CO3 (Note! The 4 and 3 are subscripts, and not coefficients)

17.6 gNH4CO3

Now to convert to mol of one of our substances we take the percent composition of that particular part of the molecule and multiply it by our starting mass. This is what it looks like using dimensional analyse.

17.6 gNH4CO3 * (Molar Mass of NH4 / Molar Mass of NH4CO3)

Grab a periodic table (or look one up) and find the molar masses for these molecules! Well. In this case I'll do it for you. (Note: I round the molar masses off to two decimal places)

NH4 = 14.01 + 4*1.01 = 18.05 g/mol
NH4CO3 = 14.01 + 4*1.01 + 12.01 + 3*16.00 = 78.06 g/mol

17.6 gNH4CO3 * (18.05 molNH4 / 78.06 molNH4CO3)
= 4.07 gNH4

Now just take the molar mass we found to convert that amount into moles!

4.07 gNH4 * (1 molNH4 / 18.05 gNH4) = 0.225 molNH4

4 0

3 years ago